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Appendix F
Segment 2- 2A and 3 - AC Induction and Mitigation Study
bull bull bull bull bull bull bull bull bull bull
ro Box 1438
(7021 Foxfire Dr- 60012-1641)
Crystat LakeH 60039 1~3g
wwwetectrosctencescam
Empire Generating Co LLC 345 kV Transmission Line Project
ACInduction Analysesfar Segments 2 2A Connector 2A and3
Prepared for Niagara Mohawk Power Corp Syracuse NY and MSE Power Systems Albany NY Prepared by John Dabkowski PhD 23 May 2008
Section
10
11
12
13
20
21
22
23
24
30
31
32
40
41
42
Table afContents
Overview
Report Outline
Transmission Line Parameters
Soil Resistivity Modeling
Electrostatic Induction
Fences and Guard Rails
Buildings
Railroads _
Electrostatic Grounding Considerations
Electromagnetic Induction
Steady State Induction
Fault Current Induction
Summary and Conclusions
Summary
Conclusions
Appendix A - Two Layer Soil Resistivity Models
Page
4
4
6
12
13
13
17
22
24
27
27
33
39
39
40
41
2
Listcflllustrauons
Eigure Page
11 Segment 2 ROW Configuration 7
12 Segment 3 ROW Configuration 8
13 Segment 2A Connector ROW Configuration 9
14 Segment 2A ROW Configuration 10
2 Electrostatic Induction On Chain Link Fences - Open Circuit Potential 15
22 Electrostatic Induction On Chain Link Fences - Short Circuit Current 15
2J Electrostatic Induction On Guard Rails - Open Circuit Potential 16
24 Electrostatic Induction On Guard Rails - Short Circuit Current 16
2 Yonder Farms Electrostatic Induction Model 17
26 National Grid Garage Complex 20
27 Generic Grounding System 26
3 Steady State Pipe Induction wo 345 kV Transmission Line - No Pipe 28
32 Steady State Induction with 345kY Transmission Line - No Pipe Mitigation 28
33a Steady State Induction with 34SkV Transmission Line - With Mitigation 30
33b Steady State Induction wlo 345 kV Transmission Line-wlMitigation 30
34a Induced Pipe Current with 345 kV Transmission Line - wMitigation 31
JAb Induced Pipe Current wlo 345 kV Transmission Line - wMitigation 32
35 Induced Pipe Current wo 345 kV Transmission Line - wlo Mitigation 32
36 345 kV Fault Induced Pipe Coating Potential- wMitigation 33
37 345 kV Fault Induced Pipe Touch Potential - wMitigation 34
38 345 kV Fault Induced Pipe Step Potentialgt- wMitigation J5
39 345 kV Fault Induced Pipe Current - wMitigation 35
310 Segment 2A Fault Induced Pipe Coating Potential- wl1itigation 37
311 Segment 2A Fault Induced Pipe Touch Potential- wMitigation 37
312 Segment 2A Fault Induced Pipe Step Potential- wMitigation 38
313 Segment 2A Faull Induced Pipe Current - wMitigation 38
3
Electrostatic amp Electromagnetic Induction Analyses
10Overview
The proposed 345 kY Empire Generating Co LLC transmission line originates at the EGCo 345 kY switchyard and terminates at the Niagara Mohawk Power Corporation (NMPC) Reynolds Road Substation The length of the transmission line is approximately 81 miles The transmission line is broken down into the following segments
1 The first segment originates at the EGCo switchyard and continues for a distance of 1Zmiles The 345 k V transmission line is mounted on a double vertical circuit pole with an existing NMPC 115 kY circuit The induction analyses for this segment were completed by Electro Sciences Inc (ESl) in the year 2006
2 The second segment starts at Tower 19 (reference-Efifo switchyard) and continues for a distance of approximately 23 miles to Tower 35 The line is collocated with two existing NMPC ll5 kY circuits
3 Segment 3 starts at Tower 38 and terminates at Reynolds Road Substation (Tower 68) a distance of approximately 41 milts It shares the right-of-way with four (4) NMPC 115 kV transmission lines and 132 kY distribution line
4 Connector Segment 2A extends for 1336 feel from Tower nos 65 through T-69 It meets with the Segment 2 right-of-way in the vicinity of Tower 35
5 Segment 2A extends for a distance of 2428 feet from Greenbush Substation to Connector Segment 2A (Tower 69)
The scope of the proposed work is to provide electrostatic and electromagnetic coupling calculations for objects on or close to the above rights-of-way to evaluate the coupling effects and to delineate recommended mitigation where required
11 Report Outline
111 Electrostatic Coupling
Electrostatic coupling is a result of the voltage gradient existing below the transmission line Its magnitude is a function of the line voltage The resulting electric field affects above ground objects that are electrically conductive such metallic buildings fences and guard rails Electrostatic coupling effects have been evaluated for the proposed 345 kY transmission line in Segments 2 and 3
If the object is insulated from earth ie not grounded it will be raised to a relatively high potential and it becomes a source of electric Current which could be hazardous to personnel If the object is
4
reasonably well grounded at one Or more locations charge leakage occurs and the electrostatic induced voltage drops to near zero
Since most objects subject to electrostatic induction win be grounded hazards from these generally become a non-issue However assuming a worst case approach ie the object not being grounded the implied hazards that is the maximum available generated (short circuit) currents have been determined Computer simulations have been made resulting in open circuit induced voltage and short circuit current estimates Simulation results are presented in report Section 2
Initial inspection of the alignments has shown that approximately thirteen fences and fenced enclosures and ten guard rails may be subject to electrostatic induction Generally these fences and guard are installed at either or both sides or a road which is crossed by the transmission line They do not always cross at right angles to the transmission line and hence can be subject to non-constant levels of induction with the vertical electric field varying along the fenceguard rail with distance from the transmission line This variation has been taken into account in the computer modeling
Buildings
Initially three building complexes have been identified as being of concern relative to electrostatic induction These are
bull A barber shopgun shop complex located near Structure 29
bull The National Grid garage complex located near Structure 49 and
bull The Yonder Farms nursery complex in the vicinity of Structures 66-67 Due to a portion of the complex being situated under the overhead conductors the induction levels must be evaluated and examined relative to personnel safety
Along the right-of-way there are numerous other buildings located within a few hundred feet of the transmission line Any consideration of the induction effects upon these objects will not be considered to be within the scope of work
Amtrak Railroad
The proposed 345 kV transmission line crosses an Amtrak railroad near Structure 20 The railroad complex is at right angles to the transmission line which eliminates magnetic field coupling problems However electrostatic field and fault conducted earth current coupling to the facilities can be a source of potential problems
Unfortunately the railroad facility configuration is unknown at the present time For example the length and locations of signaling blocks equipments used for signaling and communications along the track and whether above ground circuit conductors exist which could be subject to electrostatic coupling An initial approach to assessing the railroad equipment susceptibilities would be taken as follows
bull Obtain necessary data from the railroad track in order to construct a model delineating track blocks signaling and communication circuits
bull Determine facility induced voltage levels due to electrostatic induction and conducted earth fault currents from Structure 20 and
5
bull Present a report detailing the results of the coupling simulations to the railroad for evaluation by their engineers taking into account the type of signaling equipments in USe
This phase of the study has not been started due to the information required to construct a realistic computer simulation model is not presently available
112 Electromagnetic Coupling
Electromagnetic coupling is a result of currents flowing in the overhead transmission line conductors Its primary effect is to induce voltages and currents on buried facilities such as pipelines and cables sharing the common right-of-way and situated parallel to the overhead transmission lines Available alignment sheets indicate that a Dominion lz-inch diameter natural gas pipeline and a fiber optic eable run parallel to the proposed 345 kV transmission line in Segment 3 Computer modeling of this portion of the right-of-way have been made with the results presented in report Section 3
Segment 3
The above facilities will be subject to magnetic field coupling during both steady state and fault operation of the proposed 345 kV transmission line During fault periods they will also be subjected to interference arising from soil conducted currents injected by the faulted and adjacent structures through their grounding systems
Predictive coupling calculations for the steady state include magnetic field coupling contributions from all eircuits present on the right-of-way Determinations of fault current coupling levels are made for faults assumed at several locations along the right-of-way considering only the proposed 345 kV transmission line The ground potential rise of the Reynolds Road Substation as a source of interference has also been included in the fault simulations
Segment2A and Connector2A
The Dominion natural gas pipeline also parallels the overhead transmission lines in Segment 2A However no new transmission lines have been added to this Segment Hence induction effects should be of the same order of magnitude as previously existing on the right-ot-way However two pre-existing 115 kV Transmission lines have been moved to a single pole structure with a double vertical circuit configuration The result is that the distances from the transmission lines have changed The effect upon the induction levels at the pipeline has been evaluated It appears that no above ground or buried facilities exist in Connector 2A that may be subject to induction effects
12 Transmission Line Parameters
121 Rights of Way Configurations
Cross section drawings of the rights-of-way for the four segments are given in Figures 11 through 14 Structure dimensions and placing shown in the Figures were input into the computer simulation program Conductor sag was however taken into account when making the calculations
6
-1shy -
ilI ) I
i
i i J
Fig 11 Segment 2 ROW Configuration
7
_~ I _~
tdt-~~~iTk~
f r- - I -~ -- ~~gt ~iiL(f(~rE I-~~ -~~f p
l - - )lI~
-middotCr _~~
n l -lt-5
J
n----S--y-shy
~r~gtigt Ii
---~~~ r ~~_-=_1
J lii__ 1 II
Fig 12 Segment 3 ROW Configuration
8
117 stNGtI CIT nerv 1192 l(CII 57 AC5R
IIOQOI DESlGN lEtrilON
SOlJT1I
bullbull 0
oj
fAlt i
I
I I
~1J
gtbull 0
~ 0
bull bull
bull gt0
~ ~~ z
~ ltibullbullbull
~-~ g~ ~~ ~ 0
M
ll~ rbull
eo ~ I 0
Fig 13 Segment 2A Connector ROW Configuration
9
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
- I-9Jl~Uiilll -shy(rmnuHEPill HSfl9 YHnllJ
Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
bull bull bull bull bull bull bull bull bull bull
ro Box 1438
(7021 Foxfire Dr- 60012-1641)
Crystat LakeH 60039 1~3g
wwwetectrosctencescam
Empire Generating Co LLC 345 kV Transmission Line Project
ACInduction Analysesfar Segments 2 2A Connector 2A and3
Prepared for Niagara Mohawk Power Corp Syracuse NY and MSE Power Systems Albany NY Prepared by John Dabkowski PhD 23 May 2008
Section
10
11
12
13
20
21
22
23
24
30
31
32
40
41
42
Table afContents
Overview
Report Outline
Transmission Line Parameters
Soil Resistivity Modeling
Electrostatic Induction
Fences and Guard Rails
Buildings
Railroads _
Electrostatic Grounding Considerations
Electromagnetic Induction
Steady State Induction
Fault Current Induction
Summary and Conclusions
Summary
Conclusions
Appendix A - Two Layer Soil Resistivity Models
Page
4
4
6
12
13
13
17
22
24
27
27
33
39
39
40
41
2
Listcflllustrauons
Eigure Page
11 Segment 2 ROW Configuration 7
12 Segment 3 ROW Configuration 8
13 Segment 2A Connector ROW Configuration 9
14 Segment 2A ROW Configuration 10
2 Electrostatic Induction On Chain Link Fences - Open Circuit Potential 15
22 Electrostatic Induction On Chain Link Fences - Short Circuit Current 15
2J Electrostatic Induction On Guard Rails - Open Circuit Potential 16
24 Electrostatic Induction On Guard Rails - Short Circuit Current 16
2 Yonder Farms Electrostatic Induction Model 17
26 National Grid Garage Complex 20
27 Generic Grounding System 26
3 Steady State Pipe Induction wo 345 kV Transmission Line - No Pipe 28
32 Steady State Induction with 345kY Transmission Line - No Pipe Mitigation 28
33a Steady State Induction with 34SkV Transmission Line - With Mitigation 30
33b Steady State Induction wlo 345 kV Transmission Line-wlMitigation 30
34a Induced Pipe Current with 345 kV Transmission Line - wMitigation 31
JAb Induced Pipe Current wlo 345 kV Transmission Line - wMitigation 32
35 Induced Pipe Current wo 345 kV Transmission Line - wlo Mitigation 32
36 345 kV Fault Induced Pipe Coating Potential- wMitigation 33
37 345 kV Fault Induced Pipe Touch Potential - wMitigation 34
38 345 kV Fault Induced Pipe Step Potentialgt- wMitigation J5
39 345 kV Fault Induced Pipe Current - wMitigation 35
310 Segment 2A Fault Induced Pipe Coating Potential- wl1itigation 37
311 Segment 2A Fault Induced Pipe Touch Potential- wMitigation 37
312 Segment 2A Fault Induced Pipe Step Potential- wMitigation 38
313 Segment 2A Faull Induced Pipe Current - wMitigation 38
3
Electrostatic amp Electromagnetic Induction Analyses
10Overview
The proposed 345 kY Empire Generating Co LLC transmission line originates at the EGCo 345 kY switchyard and terminates at the Niagara Mohawk Power Corporation (NMPC) Reynolds Road Substation The length of the transmission line is approximately 81 miles The transmission line is broken down into the following segments
1 The first segment originates at the EGCo switchyard and continues for a distance of 1Zmiles The 345 k V transmission line is mounted on a double vertical circuit pole with an existing NMPC 115 kY circuit The induction analyses for this segment were completed by Electro Sciences Inc (ESl) in the year 2006
2 The second segment starts at Tower 19 (reference-Efifo switchyard) and continues for a distance of approximately 23 miles to Tower 35 The line is collocated with two existing NMPC ll5 kY circuits
3 Segment 3 starts at Tower 38 and terminates at Reynolds Road Substation (Tower 68) a distance of approximately 41 milts It shares the right-of-way with four (4) NMPC 115 kV transmission lines and 132 kY distribution line
4 Connector Segment 2A extends for 1336 feel from Tower nos 65 through T-69 It meets with the Segment 2 right-of-way in the vicinity of Tower 35
5 Segment 2A extends for a distance of 2428 feet from Greenbush Substation to Connector Segment 2A (Tower 69)
The scope of the proposed work is to provide electrostatic and electromagnetic coupling calculations for objects on or close to the above rights-of-way to evaluate the coupling effects and to delineate recommended mitigation where required
11 Report Outline
111 Electrostatic Coupling
Electrostatic coupling is a result of the voltage gradient existing below the transmission line Its magnitude is a function of the line voltage The resulting electric field affects above ground objects that are electrically conductive such metallic buildings fences and guard rails Electrostatic coupling effects have been evaluated for the proposed 345 kY transmission line in Segments 2 and 3
If the object is insulated from earth ie not grounded it will be raised to a relatively high potential and it becomes a source of electric Current which could be hazardous to personnel If the object is
4
reasonably well grounded at one Or more locations charge leakage occurs and the electrostatic induced voltage drops to near zero
Since most objects subject to electrostatic induction win be grounded hazards from these generally become a non-issue However assuming a worst case approach ie the object not being grounded the implied hazards that is the maximum available generated (short circuit) currents have been determined Computer simulations have been made resulting in open circuit induced voltage and short circuit current estimates Simulation results are presented in report Section 2
Initial inspection of the alignments has shown that approximately thirteen fences and fenced enclosures and ten guard rails may be subject to electrostatic induction Generally these fences and guard are installed at either or both sides or a road which is crossed by the transmission line They do not always cross at right angles to the transmission line and hence can be subject to non-constant levels of induction with the vertical electric field varying along the fenceguard rail with distance from the transmission line This variation has been taken into account in the computer modeling
Buildings
Initially three building complexes have been identified as being of concern relative to electrostatic induction These are
bull A barber shopgun shop complex located near Structure 29
bull The National Grid garage complex located near Structure 49 and
bull The Yonder Farms nursery complex in the vicinity of Structures 66-67 Due to a portion of the complex being situated under the overhead conductors the induction levels must be evaluated and examined relative to personnel safety
Along the right-of-way there are numerous other buildings located within a few hundred feet of the transmission line Any consideration of the induction effects upon these objects will not be considered to be within the scope of work
Amtrak Railroad
The proposed 345 kV transmission line crosses an Amtrak railroad near Structure 20 The railroad complex is at right angles to the transmission line which eliminates magnetic field coupling problems However electrostatic field and fault conducted earth current coupling to the facilities can be a source of potential problems
Unfortunately the railroad facility configuration is unknown at the present time For example the length and locations of signaling blocks equipments used for signaling and communications along the track and whether above ground circuit conductors exist which could be subject to electrostatic coupling An initial approach to assessing the railroad equipment susceptibilities would be taken as follows
bull Obtain necessary data from the railroad track in order to construct a model delineating track blocks signaling and communication circuits
bull Determine facility induced voltage levels due to electrostatic induction and conducted earth fault currents from Structure 20 and
5
bull Present a report detailing the results of the coupling simulations to the railroad for evaluation by their engineers taking into account the type of signaling equipments in USe
This phase of the study has not been started due to the information required to construct a realistic computer simulation model is not presently available
112 Electromagnetic Coupling
Electromagnetic coupling is a result of currents flowing in the overhead transmission line conductors Its primary effect is to induce voltages and currents on buried facilities such as pipelines and cables sharing the common right-of-way and situated parallel to the overhead transmission lines Available alignment sheets indicate that a Dominion lz-inch diameter natural gas pipeline and a fiber optic eable run parallel to the proposed 345 kV transmission line in Segment 3 Computer modeling of this portion of the right-of-way have been made with the results presented in report Section 3
Segment 3
The above facilities will be subject to magnetic field coupling during both steady state and fault operation of the proposed 345 kV transmission line During fault periods they will also be subjected to interference arising from soil conducted currents injected by the faulted and adjacent structures through their grounding systems
Predictive coupling calculations for the steady state include magnetic field coupling contributions from all eircuits present on the right-of-way Determinations of fault current coupling levels are made for faults assumed at several locations along the right-of-way considering only the proposed 345 kV transmission line The ground potential rise of the Reynolds Road Substation as a source of interference has also been included in the fault simulations
Segment2A and Connector2A
The Dominion natural gas pipeline also parallels the overhead transmission lines in Segment 2A However no new transmission lines have been added to this Segment Hence induction effects should be of the same order of magnitude as previously existing on the right-ot-way However two pre-existing 115 kV Transmission lines have been moved to a single pole structure with a double vertical circuit configuration The result is that the distances from the transmission lines have changed The effect upon the induction levels at the pipeline has been evaluated It appears that no above ground or buried facilities exist in Connector 2A that may be subject to induction effects
12 Transmission Line Parameters
121 Rights of Way Configurations
Cross section drawings of the rights-of-way for the four segments are given in Figures 11 through 14 Structure dimensions and placing shown in the Figures were input into the computer simulation program Conductor sag was however taken into account when making the calculations
6
-1shy -
ilI ) I
i
i i J
Fig 11 Segment 2 ROW Configuration
7
_~ I _~
tdt-~~~iTk~
f r- - I -~ -- ~~gt ~iiL(f(~rE I-~~ -~~f p
l - - )lI~
-middotCr _~~
n l -lt-5
J
n----S--y-shy
~r~gtigt Ii
---~~~ r ~~_-=_1
J lii__ 1 II
Fig 12 Segment 3 ROW Configuration
8
117 stNGtI CIT nerv 1192 l(CII 57 AC5R
IIOQOI DESlGN lEtrilON
SOlJT1I
bullbull 0
oj
fAlt i
I
I I
~1J
gtbull 0
~ 0
bull bull
bull gt0
~ ~~ z
~ ltibullbullbull
~-~ g~ ~~ ~ 0
M
ll~ rbull
eo ~ I 0
Fig 13 Segment 2A Connector ROW Configuration
9
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
- I-9Jl~Uiilll -shy(rmnuHEPill HSfl9 YHnllJ
Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Section
10
11
12
13
20
21
22
23
24
30
31
32
40
41
42
Table afContents
Overview
Report Outline
Transmission Line Parameters
Soil Resistivity Modeling
Electrostatic Induction
Fences and Guard Rails
Buildings
Railroads _
Electrostatic Grounding Considerations
Electromagnetic Induction
Steady State Induction
Fault Current Induction
Summary and Conclusions
Summary
Conclusions
Appendix A - Two Layer Soil Resistivity Models
Page
4
4
6
12
13
13
17
22
24
27
27
33
39
39
40
41
2
Listcflllustrauons
Eigure Page
11 Segment 2 ROW Configuration 7
12 Segment 3 ROW Configuration 8
13 Segment 2A Connector ROW Configuration 9
14 Segment 2A ROW Configuration 10
2 Electrostatic Induction On Chain Link Fences - Open Circuit Potential 15
22 Electrostatic Induction On Chain Link Fences - Short Circuit Current 15
2J Electrostatic Induction On Guard Rails - Open Circuit Potential 16
24 Electrostatic Induction On Guard Rails - Short Circuit Current 16
2 Yonder Farms Electrostatic Induction Model 17
26 National Grid Garage Complex 20
27 Generic Grounding System 26
3 Steady State Pipe Induction wo 345 kV Transmission Line - No Pipe 28
32 Steady State Induction with 345kY Transmission Line - No Pipe Mitigation 28
33a Steady State Induction with 34SkV Transmission Line - With Mitigation 30
33b Steady State Induction wlo 345 kV Transmission Line-wlMitigation 30
34a Induced Pipe Current with 345 kV Transmission Line - wMitigation 31
JAb Induced Pipe Current wlo 345 kV Transmission Line - wMitigation 32
35 Induced Pipe Current wo 345 kV Transmission Line - wlo Mitigation 32
36 345 kV Fault Induced Pipe Coating Potential- wMitigation 33
37 345 kV Fault Induced Pipe Touch Potential - wMitigation 34
38 345 kV Fault Induced Pipe Step Potentialgt- wMitigation J5
39 345 kV Fault Induced Pipe Current - wMitigation 35
310 Segment 2A Fault Induced Pipe Coating Potential- wl1itigation 37
311 Segment 2A Fault Induced Pipe Touch Potential- wMitigation 37
312 Segment 2A Fault Induced Pipe Step Potential- wMitigation 38
313 Segment 2A Faull Induced Pipe Current - wMitigation 38
3
Electrostatic amp Electromagnetic Induction Analyses
10Overview
The proposed 345 kY Empire Generating Co LLC transmission line originates at the EGCo 345 kY switchyard and terminates at the Niagara Mohawk Power Corporation (NMPC) Reynolds Road Substation The length of the transmission line is approximately 81 miles The transmission line is broken down into the following segments
1 The first segment originates at the EGCo switchyard and continues for a distance of 1Zmiles The 345 k V transmission line is mounted on a double vertical circuit pole with an existing NMPC 115 kY circuit The induction analyses for this segment were completed by Electro Sciences Inc (ESl) in the year 2006
2 The second segment starts at Tower 19 (reference-Efifo switchyard) and continues for a distance of approximately 23 miles to Tower 35 The line is collocated with two existing NMPC ll5 kY circuits
3 Segment 3 starts at Tower 38 and terminates at Reynolds Road Substation (Tower 68) a distance of approximately 41 milts It shares the right-of-way with four (4) NMPC 115 kV transmission lines and 132 kY distribution line
4 Connector Segment 2A extends for 1336 feel from Tower nos 65 through T-69 It meets with the Segment 2 right-of-way in the vicinity of Tower 35
5 Segment 2A extends for a distance of 2428 feet from Greenbush Substation to Connector Segment 2A (Tower 69)
The scope of the proposed work is to provide electrostatic and electromagnetic coupling calculations for objects on or close to the above rights-of-way to evaluate the coupling effects and to delineate recommended mitigation where required
11 Report Outline
111 Electrostatic Coupling
Electrostatic coupling is a result of the voltage gradient existing below the transmission line Its magnitude is a function of the line voltage The resulting electric field affects above ground objects that are electrically conductive such metallic buildings fences and guard rails Electrostatic coupling effects have been evaluated for the proposed 345 kY transmission line in Segments 2 and 3
If the object is insulated from earth ie not grounded it will be raised to a relatively high potential and it becomes a source of electric Current which could be hazardous to personnel If the object is
4
reasonably well grounded at one Or more locations charge leakage occurs and the electrostatic induced voltage drops to near zero
Since most objects subject to electrostatic induction win be grounded hazards from these generally become a non-issue However assuming a worst case approach ie the object not being grounded the implied hazards that is the maximum available generated (short circuit) currents have been determined Computer simulations have been made resulting in open circuit induced voltage and short circuit current estimates Simulation results are presented in report Section 2
Initial inspection of the alignments has shown that approximately thirteen fences and fenced enclosures and ten guard rails may be subject to electrostatic induction Generally these fences and guard are installed at either or both sides or a road which is crossed by the transmission line They do not always cross at right angles to the transmission line and hence can be subject to non-constant levels of induction with the vertical electric field varying along the fenceguard rail with distance from the transmission line This variation has been taken into account in the computer modeling
Buildings
Initially three building complexes have been identified as being of concern relative to electrostatic induction These are
bull A barber shopgun shop complex located near Structure 29
bull The National Grid garage complex located near Structure 49 and
bull The Yonder Farms nursery complex in the vicinity of Structures 66-67 Due to a portion of the complex being situated under the overhead conductors the induction levels must be evaluated and examined relative to personnel safety
Along the right-of-way there are numerous other buildings located within a few hundred feet of the transmission line Any consideration of the induction effects upon these objects will not be considered to be within the scope of work
Amtrak Railroad
The proposed 345 kV transmission line crosses an Amtrak railroad near Structure 20 The railroad complex is at right angles to the transmission line which eliminates magnetic field coupling problems However electrostatic field and fault conducted earth current coupling to the facilities can be a source of potential problems
Unfortunately the railroad facility configuration is unknown at the present time For example the length and locations of signaling blocks equipments used for signaling and communications along the track and whether above ground circuit conductors exist which could be subject to electrostatic coupling An initial approach to assessing the railroad equipment susceptibilities would be taken as follows
bull Obtain necessary data from the railroad track in order to construct a model delineating track blocks signaling and communication circuits
bull Determine facility induced voltage levels due to electrostatic induction and conducted earth fault currents from Structure 20 and
5
bull Present a report detailing the results of the coupling simulations to the railroad for evaluation by their engineers taking into account the type of signaling equipments in USe
This phase of the study has not been started due to the information required to construct a realistic computer simulation model is not presently available
112 Electromagnetic Coupling
Electromagnetic coupling is a result of currents flowing in the overhead transmission line conductors Its primary effect is to induce voltages and currents on buried facilities such as pipelines and cables sharing the common right-of-way and situated parallel to the overhead transmission lines Available alignment sheets indicate that a Dominion lz-inch diameter natural gas pipeline and a fiber optic eable run parallel to the proposed 345 kV transmission line in Segment 3 Computer modeling of this portion of the right-of-way have been made with the results presented in report Section 3
Segment 3
The above facilities will be subject to magnetic field coupling during both steady state and fault operation of the proposed 345 kV transmission line During fault periods they will also be subjected to interference arising from soil conducted currents injected by the faulted and adjacent structures through their grounding systems
Predictive coupling calculations for the steady state include magnetic field coupling contributions from all eircuits present on the right-of-way Determinations of fault current coupling levels are made for faults assumed at several locations along the right-of-way considering only the proposed 345 kV transmission line The ground potential rise of the Reynolds Road Substation as a source of interference has also been included in the fault simulations
Segment2A and Connector2A
The Dominion natural gas pipeline also parallels the overhead transmission lines in Segment 2A However no new transmission lines have been added to this Segment Hence induction effects should be of the same order of magnitude as previously existing on the right-ot-way However two pre-existing 115 kV Transmission lines have been moved to a single pole structure with a double vertical circuit configuration The result is that the distances from the transmission lines have changed The effect upon the induction levels at the pipeline has been evaluated It appears that no above ground or buried facilities exist in Connector 2A that may be subject to induction effects
12 Transmission Line Parameters
121 Rights of Way Configurations
Cross section drawings of the rights-of-way for the four segments are given in Figures 11 through 14 Structure dimensions and placing shown in the Figures were input into the computer simulation program Conductor sag was however taken into account when making the calculations
6
-1shy -
ilI ) I
i
i i J
Fig 11 Segment 2 ROW Configuration
7
_~ I _~
tdt-~~~iTk~
f r- - I -~ -- ~~gt ~iiL(f(~rE I-~~ -~~f p
l - - )lI~
-middotCr _~~
n l -lt-5
J
n----S--y-shy
~r~gtigt Ii
---~~~ r ~~_-=_1
J lii__ 1 II
Fig 12 Segment 3 ROW Configuration
8
117 stNGtI CIT nerv 1192 l(CII 57 AC5R
IIOQOI DESlGN lEtrilON
SOlJT1I
bullbull 0
oj
fAlt i
I
I I
~1J
gtbull 0
~ 0
bull bull
bull gt0
~ ~~ z
~ ltibullbullbull
~-~ g~ ~~ ~ 0
M
ll~ rbull
eo ~ I 0
Fig 13 Segment 2A Connector ROW Configuration
9
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
- I-9Jl~Uiilll -shy(rmnuHEPill HSfl9 YHnllJ
Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
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48
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55
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56
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58
Listcflllustrauons
Eigure Page
11 Segment 2 ROW Configuration 7
12 Segment 3 ROW Configuration 8
13 Segment 2A Connector ROW Configuration 9
14 Segment 2A ROW Configuration 10
2 Electrostatic Induction On Chain Link Fences - Open Circuit Potential 15
22 Electrostatic Induction On Chain Link Fences - Short Circuit Current 15
2J Electrostatic Induction On Guard Rails - Open Circuit Potential 16
24 Electrostatic Induction On Guard Rails - Short Circuit Current 16
2 Yonder Farms Electrostatic Induction Model 17
26 National Grid Garage Complex 20
27 Generic Grounding System 26
3 Steady State Pipe Induction wo 345 kV Transmission Line - No Pipe 28
32 Steady State Induction with 345kY Transmission Line - No Pipe Mitigation 28
33a Steady State Induction with 34SkV Transmission Line - With Mitigation 30
33b Steady State Induction wlo 345 kV Transmission Line-wlMitigation 30
34a Induced Pipe Current with 345 kV Transmission Line - wMitigation 31
JAb Induced Pipe Current wlo 345 kV Transmission Line - wMitigation 32
35 Induced Pipe Current wo 345 kV Transmission Line - wlo Mitigation 32
36 345 kV Fault Induced Pipe Coating Potential- wMitigation 33
37 345 kV Fault Induced Pipe Touch Potential - wMitigation 34
38 345 kV Fault Induced Pipe Step Potentialgt- wMitigation J5
39 345 kV Fault Induced Pipe Current - wMitigation 35
310 Segment 2A Fault Induced Pipe Coating Potential- wl1itigation 37
311 Segment 2A Fault Induced Pipe Touch Potential- wMitigation 37
312 Segment 2A Fault Induced Pipe Step Potential- wMitigation 38
313 Segment 2A Faull Induced Pipe Current - wMitigation 38
3
Electrostatic amp Electromagnetic Induction Analyses
10Overview
The proposed 345 kY Empire Generating Co LLC transmission line originates at the EGCo 345 kY switchyard and terminates at the Niagara Mohawk Power Corporation (NMPC) Reynolds Road Substation The length of the transmission line is approximately 81 miles The transmission line is broken down into the following segments
1 The first segment originates at the EGCo switchyard and continues for a distance of 1Zmiles The 345 k V transmission line is mounted on a double vertical circuit pole with an existing NMPC 115 kY circuit The induction analyses for this segment were completed by Electro Sciences Inc (ESl) in the year 2006
2 The second segment starts at Tower 19 (reference-Efifo switchyard) and continues for a distance of approximately 23 miles to Tower 35 The line is collocated with two existing NMPC ll5 kY circuits
3 Segment 3 starts at Tower 38 and terminates at Reynolds Road Substation (Tower 68) a distance of approximately 41 milts It shares the right-of-way with four (4) NMPC 115 kV transmission lines and 132 kY distribution line
4 Connector Segment 2A extends for 1336 feel from Tower nos 65 through T-69 It meets with the Segment 2 right-of-way in the vicinity of Tower 35
5 Segment 2A extends for a distance of 2428 feet from Greenbush Substation to Connector Segment 2A (Tower 69)
The scope of the proposed work is to provide electrostatic and electromagnetic coupling calculations for objects on or close to the above rights-of-way to evaluate the coupling effects and to delineate recommended mitigation where required
11 Report Outline
111 Electrostatic Coupling
Electrostatic coupling is a result of the voltage gradient existing below the transmission line Its magnitude is a function of the line voltage The resulting electric field affects above ground objects that are electrically conductive such metallic buildings fences and guard rails Electrostatic coupling effects have been evaluated for the proposed 345 kY transmission line in Segments 2 and 3
If the object is insulated from earth ie not grounded it will be raised to a relatively high potential and it becomes a source of electric Current which could be hazardous to personnel If the object is
4
reasonably well grounded at one Or more locations charge leakage occurs and the electrostatic induced voltage drops to near zero
Since most objects subject to electrostatic induction win be grounded hazards from these generally become a non-issue However assuming a worst case approach ie the object not being grounded the implied hazards that is the maximum available generated (short circuit) currents have been determined Computer simulations have been made resulting in open circuit induced voltage and short circuit current estimates Simulation results are presented in report Section 2
Initial inspection of the alignments has shown that approximately thirteen fences and fenced enclosures and ten guard rails may be subject to electrostatic induction Generally these fences and guard are installed at either or both sides or a road which is crossed by the transmission line They do not always cross at right angles to the transmission line and hence can be subject to non-constant levels of induction with the vertical electric field varying along the fenceguard rail with distance from the transmission line This variation has been taken into account in the computer modeling
Buildings
Initially three building complexes have been identified as being of concern relative to electrostatic induction These are
bull A barber shopgun shop complex located near Structure 29
bull The National Grid garage complex located near Structure 49 and
bull The Yonder Farms nursery complex in the vicinity of Structures 66-67 Due to a portion of the complex being situated under the overhead conductors the induction levels must be evaluated and examined relative to personnel safety
Along the right-of-way there are numerous other buildings located within a few hundred feet of the transmission line Any consideration of the induction effects upon these objects will not be considered to be within the scope of work
Amtrak Railroad
The proposed 345 kV transmission line crosses an Amtrak railroad near Structure 20 The railroad complex is at right angles to the transmission line which eliminates magnetic field coupling problems However electrostatic field and fault conducted earth current coupling to the facilities can be a source of potential problems
Unfortunately the railroad facility configuration is unknown at the present time For example the length and locations of signaling blocks equipments used for signaling and communications along the track and whether above ground circuit conductors exist which could be subject to electrostatic coupling An initial approach to assessing the railroad equipment susceptibilities would be taken as follows
bull Obtain necessary data from the railroad track in order to construct a model delineating track blocks signaling and communication circuits
bull Determine facility induced voltage levels due to electrostatic induction and conducted earth fault currents from Structure 20 and
5
bull Present a report detailing the results of the coupling simulations to the railroad for evaluation by their engineers taking into account the type of signaling equipments in USe
This phase of the study has not been started due to the information required to construct a realistic computer simulation model is not presently available
112 Electromagnetic Coupling
Electromagnetic coupling is a result of currents flowing in the overhead transmission line conductors Its primary effect is to induce voltages and currents on buried facilities such as pipelines and cables sharing the common right-of-way and situated parallel to the overhead transmission lines Available alignment sheets indicate that a Dominion lz-inch diameter natural gas pipeline and a fiber optic eable run parallel to the proposed 345 kV transmission line in Segment 3 Computer modeling of this portion of the right-of-way have been made with the results presented in report Section 3
Segment 3
The above facilities will be subject to magnetic field coupling during both steady state and fault operation of the proposed 345 kV transmission line During fault periods they will also be subjected to interference arising from soil conducted currents injected by the faulted and adjacent structures through their grounding systems
Predictive coupling calculations for the steady state include magnetic field coupling contributions from all eircuits present on the right-of-way Determinations of fault current coupling levels are made for faults assumed at several locations along the right-of-way considering only the proposed 345 kV transmission line The ground potential rise of the Reynolds Road Substation as a source of interference has also been included in the fault simulations
Segment2A and Connector2A
The Dominion natural gas pipeline also parallels the overhead transmission lines in Segment 2A However no new transmission lines have been added to this Segment Hence induction effects should be of the same order of magnitude as previously existing on the right-ot-way However two pre-existing 115 kV Transmission lines have been moved to a single pole structure with a double vertical circuit configuration The result is that the distances from the transmission lines have changed The effect upon the induction levels at the pipeline has been evaluated It appears that no above ground or buried facilities exist in Connector 2A that may be subject to induction effects
12 Transmission Line Parameters
121 Rights of Way Configurations
Cross section drawings of the rights-of-way for the four segments are given in Figures 11 through 14 Structure dimensions and placing shown in the Figures were input into the computer simulation program Conductor sag was however taken into account when making the calculations
6
-1shy -
ilI ) I
i
i i J
Fig 11 Segment 2 ROW Configuration
7
_~ I _~
tdt-~~~iTk~
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l - - )lI~
-middotCr _~~
n l -lt-5
J
n----S--y-shy
~r~gtigt Ii
---~~~ r ~~_-=_1
J lii__ 1 II
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8
117 stNGtI CIT nerv 1192 l(CII 57 AC5R
IIOQOI DESlGN lEtrilON
SOlJT1I
bullbull 0
oj
fAlt i
I
I I
~1J
gtbull 0
~ 0
bull bull
bull gt0
~ ~~ z
~ ltibullbullbull
~-~ g~ ~~ ~ 0
M
ll~ rbull
eo ~ I 0
Fig 13 Segment 2A Connector ROW Configuration
9
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
- I-9Jl~Uiilll -shy(rmnuHEPill HSfl9 YHnllJ
Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
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Electrostatic amp Electromagnetic Induction Analyses
10Overview
The proposed 345 kY Empire Generating Co LLC transmission line originates at the EGCo 345 kY switchyard and terminates at the Niagara Mohawk Power Corporation (NMPC) Reynolds Road Substation The length of the transmission line is approximately 81 miles The transmission line is broken down into the following segments
1 The first segment originates at the EGCo switchyard and continues for a distance of 1Zmiles The 345 k V transmission line is mounted on a double vertical circuit pole with an existing NMPC 115 kY circuit The induction analyses for this segment were completed by Electro Sciences Inc (ESl) in the year 2006
2 The second segment starts at Tower 19 (reference-Efifo switchyard) and continues for a distance of approximately 23 miles to Tower 35 The line is collocated with two existing NMPC ll5 kY circuits
3 Segment 3 starts at Tower 38 and terminates at Reynolds Road Substation (Tower 68) a distance of approximately 41 milts It shares the right-of-way with four (4) NMPC 115 kV transmission lines and 132 kY distribution line
4 Connector Segment 2A extends for 1336 feel from Tower nos 65 through T-69 It meets with the Segment 2 right-of-way in the vicinity of Tower 35
5 Segment 2A extends for a distance of 2428 feet from Greenbush Substation to Connector Segment 2A (Tower 69)
The scope of the proposed work is to provide electrostatic and electromagnetic coupling calculations for objects on or close to the above rights-of-way to evaluate the coupling effects and to delineate recommended mitigation where required
11 Report Outline
111 Electrostatic Coupling
Electrostatic coupling is a result of the voltage gradient existing below the transmission line Its magnitude is a function of the line voltage The resulting electric field affects above ground objects that are electrically conductive such metallic buildings fences and guard rails Electrostatic coupling effects have been evaluated for the proposed 345 kY transmission line in Segments 2 and 3
If the object is insulated from earth ie not grounded it will be raised to a relatively high potential and it becomes a source of electric Current which could be hazardous to personnel If the object is
4
reasonably well grounded at one Or more locations charge leakage occurs and the electrostatic induced voltage drops to near zero
Since most objects subject to electrostatic induction win be grounded hazards from these generally become a non-issue However assuming a worst case approach ie the object not being grounded the implied hazards that is the maximum available generated (short circuit) currents have been determined Computer simulations have been made resulting in open circuit induced voltage and short circuit current estimates Simulation results are presented in report Section 2
Initial inspection of the alignments has shown that approximately thirteen fences and fenced enclosures and ten guard rails may be subject to electrostatic induction Generally these fences and guard are installed at either or both sides or a road which is crossed by the transmission line They do not always cross at right angles to the transmission line and hence can be subject to non-constant levels of induction with the vertical electric field varying along the fenceguard rail with distance from the transmission line This variation has been taken into account in the computer modeling
Buildings
Initially three building complexes have been identified as being of concern relative to electrostatic induction These are
bull A barber shopgun shop complex located near Structure 29
bull The National Grid garage complex located near Structure 49 and
bull The Yonder Farms nursery complex in the vicinity of Structures 66-67 Due to a portion of the complex being situated under the overhead conductors the induction levels must be evaluated and examined relative to personnel safety
Along the right-of-way there are numerous other buildings located within a few hundred feet of the transmission line Any consideration of the induction effects upon these objects will not be considered to be within the scope of work
Amtrak Railroad
The proposed 345 kV transmission line crosses an Amtrak railroad near Structure 20 The railroad complex is at right angles to the transmission line which eliminates magnetic field coupling problems However electrostatic field and fault conducted earth current coupling to the facilities can be a source of potential problems
Unfortunately the railroad facility configuration is unknown at the present time For example the length and locations of signaling blocks equipments used for signaling and communications along the track and whether above ground circuit conductors exist which could be subject to electrostatic coupling An initial approach to assessing the railroad equipment susceptibilities would be taken as follows
bull Obtain necessary data from the railroad track in order to construct a model delineating track blocks signaling and communication circuits
bull Determine facility induced voltage levels due to electrostatic induction and conducted earth fault currents from Structure 20 and
5
bull Present a report detailing the results of the coupling simulations to the railroad for evaluation by their engineers taking into account the type of signaling equipments in USe
This phase of the study has not been started due to the information required to construct a realistic computer simulation model is not presently available
112 Electromagnetic Coupling
Electromagnetic coupling is a result of currents flowing in the overhead transmission line conductors Its primary effect is to induce voltages and currents on buried facilities such as pipelines and cables sharing the common right-of-way and situated parallel to the overhead transmission lines Available alignment sheets indicate that a Dominion lz-inch diameter natural gas pipeline and a fiber optic eable run parallel to the proposed 345 kV transmission line in Segment 3 Computer modeling of this portion of the right-of-way have been made with the results presented in report Section 3
Segment 3
The above facilities will be subject to magnetic field coupling during both steady state and fault operation of the proposed 345 kV transmission line During fault periods they will also be subjected to interference arising from soil conducted currents injected by the faulted and adjacent structures through their grounding systems
Predictive coupling calculations for the steady state include magnetic field coupling contributions from all eircuits present on the right-of-way Determinations of fault current coupling levels are made for faults assumed at several locations along the right-of-way considering only the proposed 345 kV transmission line The ground potential rise of the Reynolds Road Substation as a source of interference has also been included in the fault simulations
Segment2A and Connector2A
The Dominion natural gas pipeline also parallels the overhead transmission lines in Segment 2A However no new transmission lines have been added to this Segment Hence induction effects should be of the same order of magnitude as previously existing on the right-ot-way However two pre-existing 115 kV Transmission lines have been moved to a single pole structure with a double vertical circuit configuration The result is that the distances from the transmission lines have changed The effect upon the induction levels at the pipeline has been evaluated It appears that no above ground or buried facilities exist in Connector 2A that may be subject to induction effects
12 Transmission Line Parameters
121 Rights of Way Configurations
Cross section drawings of the rights-of-way for the four segments are given in Figures 11 through 14 Structure dimensions and placing shown in the Figures were input into the computer simulation program Conductor sag was however taken into account when making the calculations
6
-1shy -
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i
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7
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8
117 stNGtI CIT nerv 1192 l(CII 57 AC5R
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bull gt0
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9
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
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Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
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10 100 1000
Wenner Measurement Pin Spacing shy meters
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43
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44
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46
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47
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48
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10011
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52
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100[1
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layer Depth - meters
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C~_IllP_lIte_~_Moder__- L_ay~r 11_2
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53
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55
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56
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58
reasonably well grounded at one Or more locations charge leakage occurs and the electrostatic induced voltage drops to near zero
Since most objects subject to electrostatic induction win be grounded hazards from these generally become a non-issue However assuming a worst case approach ie the object not being grounded the implied hazards that is the maximum available generated (short circuit) currents have been determined Computer simulations have been made resulting in open circuit induced voltage and short circuit current estimates Simulation results are presented in report Section 2
Initial inspection of the alignments has shown that approximately thirteen fences and fenced enclosures and ten guard rails may be subject to electrostatic induction Generally these fences and guard are installed at either or both sides or a road which is crossed by the transmission line They do not always cross at right angles to the transmission line and hence can be subject to non-constant levels of induction with the vertical electric field varying along the fenceguard rail with distance from the transmission line This variation has been taken into account in the computer modeling
Buildings
Initially three building complexes have been identified as being of concern relative to electrostatic induction These are
bull A barber shopgun shop complex located near Structure 29
bull The National Grid garage complex located near Structure 49 and
bull The Yonder Farms nursery complex in the vicinity of Structures 66-67 Due to a portion of the complex being situated under the overhead conductors the induction levels must be evaluated and examined relative to personnel safety
Along the right-of-way there are numerous other buildings located within a few hundred feet of the transmission line Any consideration of the induction effects upon these objects will not be considered to be within the scope of work
Amtrak Railroad
The proposed 345 kV transmission line crosses an Amtrak railroad near Structure 20 The railroad complex is at right angles to the transmission line which eliminates magnetic field coupling problems However electrostatic field and fault conducted earth current coupling to the facilities can be a source of potential problems
Unfortunately the railroad facility configuration is unknown at the present time For example the length and locations of signaling blocks equipments used for signaling and communications along the track and whether above ground circuit conductors exist which could be subject to electrostatic coupling An initial approach to assessing the railroad equipment susceptibilities would be taken as follows
bull Obtain necessary data from the railroad track in order to construct a model delineating track blocks signaling and communication circuits
bull Determine facility induced voltage levels due to electrostatic induction and conducted earth fault currents from Structure 20 and
5
bull Present a report detailing the results of the coupling simulations to the railroad for evaluation by their engineers taking into account the type of signaling equipments in USe
This phase of the study has not been started due to the information required to construct a realistic computer simulation model is not presently available
112 Electromagnetic Coupling
Electromagnetic coupling is a result of currents flowing in the overhead transmission line conductors Its primary effect is to induce voltages and currents on buried facilities such as pipelines and cables sharing the common right-of-way and situated parallel to the overhead transmission lines Available alignment sheets indicate that a Dominion lz-inch diameter natural gas pipeline and a fiber optic eable run parallel to the proposed 345 kV transmission line in Segment 3 Computer modeling of this portion of the right-of-way have been made with the results presented in report Section 3
Segment 3
The above facilities will be subject to magnetic field coupling during both steady state and fault operation of the proposed 345 kV transmission line During fault periods they will also be subjected to interference arising from soil conducted currents injected by the faulted and adjacent structures through their grounding systems
Predictive coupling calculations for the steady state include magnetic field coupling contributions from all eircuits present on the right-of-way Determinations of fault current coupling levels are made for faults assumed at several locations along the right-of-way considering only the proposed 345 kV transmission line The ground potential rise of the Reynolds Road Substation as a source of interference has also been included in the fault simulations
Segment2A and Connector2A
The Dominion natural gas pipeline also parallels the overhead transmission lines in Segment 2A However no new transmission lines have been added to this Segment Hence induction effects should be of the same order of magnitude as previously existing on the right-ot-way However two pre-existing 115 kV Transmission lines have been moved to a single pole structure with a double vertical circuit configuration The result is that the distances from the transmission lines have changed The effect upon the induction levels at the pipeline has been evaluated It appears that no above ground or buried facilities exist in Connector 2A that may be subject to induction effects
12 Transmission Line Parameters
121 Rights of Way Configurations
Cross section drawings of the rights-of-way for the four segments are given in Figures 11 through 14 Structure dimensions and placing shown in the Figures were input into the computer simulation program Conductor sag was however taken into account when making the calculations
6
-1shy -
ilI ) I
i
i i J
Fig 11 Segment 2 ROW Configuration
7
_~ I _~
tdt-~~~iTk~
f r- - I -~ -- ~~gt ~iiL(f(~rE I-~~ -~~f p
l - - )lI~
-middotCr _~~
n l -lt-5
J
n----S--y-shy
~r~gtigt Ii
---~~~ r ~~_-=_1
J lii__ 1 II
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8
117 stNGtI CIT nerv 1192 l(CII 57 AC5R
IIOQOI DESlGN lEtrilON
SOlJT1I
bullbull 0
oj
fAlt i
I
I I
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gtbull 0
~ 0
bull bull
bull gt0
~ ~~ z
~ ltibullbullbull
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M
ll~ rbull
eo ~ I 0
Fig 13 Segment 2A Connector ROW Configuration
9
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
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Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
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th
Computed Model -layer 1
126
Computed Uodel - layer 2
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10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
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I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
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Con-pIted Model - Lrer~ 2
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100 ~O--------~---------(o-~----~--i100 10000
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45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
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46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
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Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
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-------------
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Computed Mod~1 - lay~r II- 1
1000
ne sts
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TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
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Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
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I
Computed MOdel - lityer bull 1
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teau
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49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
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LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
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50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
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Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
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Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
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layer Depth _ meters n
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100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
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layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
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54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
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10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
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TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
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Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
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10000
lt
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1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
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Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
bull Present a report detailing the results of the coupling simulations to the railroad for evaluation by their engineers taking into account the type of signaling equipments in USe
This phase of the study has not been started due to the information required to construct a realistic computer simulation model is not presently available
112 Electromagnetic Coupling
Electromagnetic coupling is a result of currents flowing in the overhead transmission line conductors Its primary effect is to induce voltages and currents on buried facilities such as pipelines and cables sharing the common right-of-way and situated parallel to the overhead transmission lines Available alignment sheets indicate that a Dominion lz-inch diameter natural gas pipeline and a fiber optic eable run parallel to the proposed 345 kV transmission line in Segment 3 Computer modeling of this portion of the right-of-way have been made with the results presented in report Section 3
Segment 3
The above facilities will be subject to magnetic field coupling during both steady state and fault operation of the proposed 345 kV transmission line During fault periods they will also be subjected to interference arising from soil conducted currents injected by the faulted and adjacent structures through their grounding systems
Predictive coupling calculations for the steady state include magnetic field coupling contributions from all eircuits present on the right-of-way Determinations of fault current coupling levels are made for faults assumed at several locations along the right-of-way considering only the proposed 345 kV transmission line The ground potential rise of the Reynolds Road Substation as a source of interference has also been included in the fault simulations
Segment2A and Connector2A
The Dominion natural gas pipeline also parallels the overhead transmission lines in Segment 2A However no new transmission lines have been added to this Segment Hence induction effects should be of the same order of magnitude as previously existing on the right-ot-way However two pre-existing 115 kV Transmission lines have been moved to a single pole structure with a double vertical circuit configuration The result is that the distances from the transmission lines have changed The effect upon the induction levels at the pipeline has been evaluated It appears that no above ground or buried facilities exist in Connector 2A that may be subject to induction effects
12 Transmission Line Parameters
121 Rights of Way Configurations
Cross section drawings of the rights-of-way for the four segments are given in Figures 11 through 14 Structure dimensions and placing shown in the Figures were input into the computer simulation program Conductor sag was however taken into account when making the calculations
6
-1shy -
ilI ) I
i
i i J
Fig 11 Segment 2 ROW Configuration
7
_~ I _~
tdt-~~~iTk~
f r- - I -~ -- ~~gt ~iiL(f(~rE I-~~ -~~f p
l - - )lI~
-middotCr _~~
n l -lt-5
J
n----S--y-shy
~r~gtigt Ii
---~~~ r ~~_-=_1
J lii__ 1 II
Fig 12 Segment 3 ROW Configuration
8
117 stNGtI CIT nerv 1192 l(CII 57 AC5R
IIOQOI DESlGN lEtrilON
SOlJT1I
bullbull 0
oj
fAlt i
I
I I
~1J
gtbull 0
~ 0
bull bull
bull gt0
~ ~~ z
~ ltibullbullbull
~-~ g~ ~~ ~ 0
M
ll~ rbull
eo ~ I 0
Fig 13 Segment 2A Connector ROW Configuration
9
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
- I-9Jl~Uiilll -shy(rmnuHEPill HSfl9 YHnllJ
Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
-1shy -
ilI ) I
i
i i J
Fig 11 Segment 2 ROW Configuration
7
_~ I _~
tdt-~~~iTk~
f r- - I -~ -- ~~gt ~iiL(f(~rE I-~~ -~~f p
l - - )lI~
-middotCr _~~
n l -lt-5
J
n----S--y-shy
~r~gtigt Ii
---~~~ r ~~_-=_1
J lii__ 1 II
Fig 12 Segment 3 ROW Configuration
8
117 stNGtI CIT nerv 1192 l(CII 57 AC5R
IIOQOI DESlGN lEtrilON
SOlJT1I
bullbull 0
oj
fAlt i
I
I I
~1J
gtbull 0
~ 0
bull bull
bull gt0
~ ~~ z
~ ltibullbullbull
~-~ g~ ~~ ~ 0
M
ll~ rbull
eo ~ I 0
Fig 13 Segment 2A Connector ROW Configuration
9
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
- I-9Jl~Uiilll -shy(rmnuHEPill HSfl9 YHnllJ
Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
_~ I _~
tdt-~~~iTk~
f r- - I -~ -- ~~gt ~iiL(f(~rE I-~~ -~~f p
l - - )lI~
-middotCr _~~
n l -lt-5
J
n----S--y-shy
~r~gtigt Ii
---~~~ r ~~_-=_1
J lii__ 1 II
Fig 12 Segment 3 ROW Configuration
8
117 stNGtI CIT nerv 1192 l(CII 57 AC5R
IIOQOI DESlGN lEtrilON
SOlJT1I
bullbull 0
oj
fAlt i
I
I I
~1J
gtbull 0
~ 0
bull bull
bull gt0
~ ~~ z
~ ltibullbullbull
~-~ g~ ~~ ~ 0
M
ll~ rbull
eo ~ I 0
Fig 13 Segment 2A Connector ROW Configuration
9
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
- I-9Jl~Uiilll -shy(rmnuHEPill HSfl9 YHnllJ
Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
117 stNGtI CIT nerv 1192 l(CII 57 AC5R
IIOQOI DESlGN lEtrilON
SOlJT1I
bullbull 0
oj
fAlt i
I
I I
~1J
gtbull 0
~ 0
bull bull
bull gt0
~ ~~ z
~ ltibullbullbull
~-~ g~ ~~ ~ 0
M
ll~ rbull
eo ~ I 0
Fig 13 Segment 2A Connector ROW Configuration
9
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
- I-9Jl~Uiilll -shy(rmnuHEPill HSfl9 YHnllJ
Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
vrlTIIlPIJ~ rl al 6lT1QIU3lI - Il~
- I-9Jl~Uiilll -shy(rmnuHEPill HSfl9 YHnllJ
Fig 14 Segment 2A ROW Configuration
10
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
--
122 Conductor Currents
Overhead conductor currents are required for computer input in order to calculate electromagnetic induction levels For steady state induction calculations the computer simulations consider load currents carried by all the circuits on the right-of-way Load currents for the circuits are listed in Table 1
Table 11 Steady State Transmission Line Load Currents
Circuit No tad Current - A
Segment 2
345 kV -5---- 99~-
16 440
17 723
Segment 3
345 kVmiddot 5 994
4 930
9 013
Segmenl2A
-16 440
17 723
4 933
9 1013
Segment 2A Connector
16 440
17 723
Electrostatic induction calculations for the 345 kV transmission line has been based upon the voltage level of 105 pu For fault induction calculations single line to ground (SLG) fault currents used in the computer program simulations are listed in Tables 12 and 13
11
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
--
--
Table 12 SLG 345 kV Transmission Line Fault Currents
Location T Current from Curren I from Comments
Empire Reynolds-kA
Near Reynolds Rd
~miles south---c---c
55 9
c- -J------se~~6shyA
Segment 3 I
Near Empire_G_en_JLI_~_8_1__~__~ Segment I J Table 13 SLG 115 kV Transmission Line Fault Currents
Comments Total Faull iirCUit No1
FLocation Current - kAI
Circuit 9
Greenbush 345 290 kA from Substation
348 296 kA from Reynolds Rd Ie Reynolds Rd
iCircuit 17
--345 I
Greenbush 323 kA from Substation
c-Feura Bush 282 268 kA from Greenbush
--Circuit 16
roreenb~1 345 ~ kA from SUbstatin
L kA from Greenbush SUbJ~nsselaer cogen1 t45
13 Soil Resistivity Modeling
From soil resistivity measurements data provided by MSE two-layer soil models were derived The models are diagrammed in Appendix A Data measurements were made by the Wenner Method with pin spacing ranging from 25 to 40 feet
12
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
20 Electrostatic Induction
Electrostatic computer simulations have been made on the basis of the line voltage for the 345 kY transmission line set to 105 pu For above ground conducting objects parallel to the transmission line the vertical electric field is constant over its length When the objects are at an angle to the transmission line the electric field magnitude varies along the object For this situation the object is sectionalized and the vertical electric field is calculated for each section The open circuit voltage and short circuit current of the object are calculated by summing the individuaI contributions from each section taking into account the varying phase of the electric field
21 Fences and Guard Rails
Along the right-of-way especially at road crossings numerous fences and guard rails are crossed Modeling each individually would be a laborious task and hence a universal model has been developed for each of these objects The open circuit voltage and short circuit current are dependent upon the following factors
bull The surface area height and length of the object
bull The crossing angle with respect to the 345 kV horizontally configured transmission line and
bull The relative position of the object with respect to the line
For a specified type of object the surface area per unit length and height do not vary significantly and hence length is the primary variable The position of the object relative to the transmission line is an important parameter For example if the transmission line center conductor is directly over the center of the Object induction levels will be smaller due to the fact that the phase of the electric field is not constant from one side of the transmission line to the other with phase cancellation occurring Higher induction levels are obtained if the object is to one side of the line with the highest obtained if the center phase conductor is directly over one end of the object This is the worst case and the one considered here
Computer simulation results are plotted respectively for metallic fences and guard rails in Figures 21 through 24 Open circuit voltages and short circuit currents are plotted as a function of fence or guard rail length and crossing angle The plots are based upon an actual not average height of seven (7) feet for the fences and Su-inches for the guard rails Small deviations from these values do not significantly alter the results
In general the plots show that a significant voltage level can be reached if the object is not mitigated (grounded) Hence a startle annoying condition is present since a spark can occur upon personnel contact More importantly however is the fact that the short circuit currents without mitigation do not reach the National Electrical Safety Code limit of five (5) milliamperes NMPC has mitigation procedures in place for the grounding of metallic fences and guard rails during construction Hence after protective procedure emplacement electrostatic induction to these objects should not pose a hazard or annoyance to personnel
Details of the grounding procedure implemented by Niagara Mohawk are as follows
bull Fenceguard rail grounding to extend 150 feet to each side ofthc centerline of crossing A ground connecting wire (2 AWG 7 strand Cu HD 45 mils PE) buried at a depth of 18 inches over this length
13
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
bull A coppcrweld vertical ground rod to be connected to the horizontal connecting wire at thirty foot intervals
bull Connection of metallic fenceguard rail posts to the horizontal connecting wire at centerline of crossing and at every third post
bull For metallic fences with non-metallic posts the fence itself shall be grounded at the centerline of crossing and at every third post
Alignment sheet identifiable guard rails and fences crossing the 345 kV transmission line in Segments 2 and 3 are listed in the following table
Table 21 Identified Guard Rail and Fence Crossings
I ncatinn Approximate CommentsType
Length - feel
Fence north of line crossing Fence NY State Route 9J 260
Guard Rail US Ruutes 9 amp 20 520 320 feet north 200 feet south
Fence Stock Lane 310 Approximately Centered
-~ Guard Rail Red Mill Road 420 160 feet north 260 feel south
Fences (2) US Route 90 1810 890 feel north 920 feet south
1720 860 feet north 860 feet south
Fences (2) NY State Route 43 780 380 feel north 400 feet south
1060 540 feet north 520 feet south
Guard Rails (2) NY Stale Route 43 910 360 feet north 550 feet south
440 300 feet north 140 feet south
Guard Rail NY State Route 4 340 160 feet north 180 feet south
Fence NY Slate Route 4 990 510 feet south 480 feet south
Figures 22 and 24 indicate that the above listed rails and fences will not provide a current source ofa magnitude that is hazardous to persons ie greater than five (5) mao However following Niagara Mohawk standard grounding procedures all should be grounded per specifications Such grounding will decrease open circuit fence potentials to levels which will not be annoying to persons touching the fence or rail
14
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
4000
~ 3000
~ o a
~ 2000 -c -
1000
Fig 21 Electrostatic Induction on Chain Link Fences ___~nce Potential as a Function of Crossing Angle
Fence parallel 10rrensmescn Lme _ (J
Calcuabons made tor 1 345 kV Transmission Lme
30deg
45deg
Fence perpendicular to Transmrscon Lne roo
l-----shy100 200
r-rr-rshy
300
Fence LengLh- feel
400 500
Fig 22 Electrostatic Induction on Chain Link Fences Short Circuit Current as a Function or Crossing Angle
3
Caculaboos maltl lor
345 ~V TransmisSIon Line
h~oce parallel to
T~i~Y
ro E
d c ~ u E Ex ro
2
30
o 1 -rshy r- ~f--OO---------o_~ 120 220 320 420 520
Fence Length - reet
15
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Fig 23 Electrostatic Induction on Guard Rails Rail Potential as a Function of Crossing 1vl91e---__
Rail parillilelic Transmission Line _0
3200
Calculahons made for
3451ltV TransmiHIOIl line
30middot
-- -_fO--_-
~ RM perpendicular to Transmission Lme 90
I200 ---- shy
100 200 300 400 SOD
Guard Rail length - feel
Fig 24 Electrostatic Induction on Guard Rails Short Circuit Current as a Function of Crossing Angle
Calculations made for 3 345 kll TransmiSSion Lme
Rarl parallel to
Transm-sslol) line Dmiddot --
~---~-=-=------
~ Ralll perpendlculn _ 90degJ
L___------ 120 220 320 420 520
Guard RallLenqth - feet
1
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
22 BUildings
221 Yonder Farms
As shown in Figure 25 the Yonder Farms complex is a mixture of many buildings There are several buildings physically connected namely the configurations 56 and 7 indicated in Figure 25 Hence they were modeled as a single entity as shown by the overlay of circles in the Figure A total of eight distinct units were modeled Since the individual modeling units are relatively large in area the electric field variation over the length of the object was taken into account in the computer simulations The buildings were modeled as electrically conductive half cylinders Units five six and seven are electrically continuous and have been So modeled The simulation results and building dimensions are presented in Table 22 which tabulates the calculated open circuit voltage and short circuit current for each unit
Fig 25 Yonder Farms Electrostatic Induction Model
17
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Table 21 Electrostatic Induction Levels for Yonder Farms Building Units
Building I v
Unil I volts rna
Buildiug Size - reel
LxWxH
100 x 20 x 9
47
16
31
053
8400
1 E900
I~ 116-0-0-+---+-------middotshy
1-3 4600
I 4
800 I 14
175x120x135
l16x46x 135
105 x 30 x 135
8 2300 051 96 x 26 x 115
9 800 015 95 x 28 x 115 ~~ L __--shy ___
The buildings electrical capacitances were calculated using the above dimensions Buildings Nos 1 2 and 3 are apparently slated for removal Hence calculated electrostatic induction effects for these buildings may eventually be not of consequence
The calculated open circuit voltages indicate that the unmitigated voltages arc high which would result in a considerable startle shock As a service to the public grounding to reduce the voltages to imperceptible levels should be implemented The computed short circuit current for unit no 4 is large enough to cause serious concern relative to the five (5) rna safe current limit Hence in order to provide a sufficient safety margin for the buildings in this location it is imperative that all buildings be adequately grounded with vertical ground rods Redundancy in the grounding system is necessary in order to ensure against accidental disconnection or breakage of a connection to a ground rod Details relative to the generic design of grounding systems for the above buildings are presented in Section 24
The transmission line electrostatic field magnitude may be reduced by decreasing the line voltage increasing the transmission line height or reducing the phase conductor separation Hence it is conceptually possible to provide adequate safety for personnel by modifying the transmission line configuration rather than implementing a grounding system for each building To test the practicability of such an approach computer simulations were made to test the effect of increasing the conductor height and therefore the tower height upon the short circuit current developed at each building Unfortunately the decrease in the short circuit currents was a much smaller rate than the increase in tower (conductor) height Table 21a lists the building short circuit currents developed for an increase in transmission line height by a factor of 25 That is the height of a 90 foot structure would have to be increased to 225 feet
18
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Table 2la Electrostatic Induction Short Circuit Currents for Increased Conductor Height
lBuilding Building Size - feetI
Unit rna LxWxH I
057 100x20x 9
2
1
047
3 037
4 95 x 28 x 115
5
11
138 175 x 120 x 135
h cc 116x46x135
~ 96 x 26 x 115 035 dO~ 9 012 95 x 28 x 115
Comparison of the entries in the two tables Indicates that building grounding is more practical and cost effective
Propane Gas Tank
In addition to the buildings a propane gas tank is located on the property The tank is situated approximately 23 feet south of the southern edge of greenhouse buildings nos 1 2 and 3 and 90 feet west of the transmission line center conductor Approximate dimensions of the tank are a ]5 foot length and a diameter of 4 feet Geometric modeling of the lank as a cylinder of these dimensions resulted in a calculated open circuit voltage of 690 volts and a short circuit current of 177 microamperes The short circuit current is very low and personnel hazard is not a problem However a nominal grounding is recommended to reduce the relatively high open circuit voltage to a level which is imperceptible to the touch
Grounding should be applied at each end of the tank by means ofa 58 inch by 8 foot length vertical copperweld ground rod Each rod is connected to the tank by means of a 6 AWG or larger diameter length of insulated copper wire which is cad welded to the tank
19
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
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52
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53
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54
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55
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56
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58
222 National Grid Garage Complex
An aerial view of the complex is shown in Figure 26 The dimensions of the buildings are approximately of the same order as their distances to the overhead phase conductors and the separation between the conductors Hence the computer simulation modeled the variation in the electric field over the width of the buildings The eomputed open circuit voltages and short circuit currents are provided in Table 22
Table 22 Electrostatic Induction Levels lor National Grid Garage Buildings
Garage
Buildiog
V
volts
I
Ma
Dimensions
feet
1 23000 14 90 x 60 x 145
2 7600 15 40 x 30 x 165
Figure 26 National Grid Garage Complex
20
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Table 22 indicates very high open circuit voltages and moderate short circuit currents For personnel safety in this location both buildings must be adequately grounded Grounding of the buildings is the most cost effective approach to mitigation A grounding system design for the complex is presented in Section 24 With the grounding system in place normal use of the buildings for vehicle and material storage is possible
An alternative approach to mitigating electrostatic effects could be that of altering the transmission line configuration Computer simulations were made to determine the effect of conductor height increase or conductor spacing on the building short circuit currents A snap shot of the results is given in Table 22a
Table 22 Short Circuit Currents after Transmission Line Configuration Changes
Garage
Building
I
Ma
Dimensions
feet
TL Conductor heights increased
By Thirty Percent
1 096 90x 60x 145
2 098 40 x 30 x 165
TL Conductor Spacing decreased
to seven feet
1 097 90x60x 145
2 103 40 x 30 x 165
Parking Lot Induction
An automobile parking lot used by a local business is located north of the garage complex across 3rd Avenue The closest edge of the parking lot is located approximately 75 feet west of the transmission line center conductor An induction simulation was made for a medium size automobile parked at the edge of the lot Computations indicate a vehicle open circuit voltage of 869 volts and a short circuit current of 34 microamperes The short circuit current is small enough that a personnel hazard is precluded The open circuit voltage is high enough that an annoyance shock may be experienced if the vehicle is extremely well insulated from ground Any leakage through or across the tires however will decrease the touch voltage considerably
223 GunBarber Shop Building
A joint gunbarber shop building is located on US Routes 9 amp20 just south of Structure 29 and approximately 100 feet north of the transmission line center conductor Visual inspection of the buiIding has shown that the building is brick with asphalt roof shingles Hence the building is nonshy
21
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
conductive and does not allow electrical charge movement on its exterior The external transmission line vertical eleetric field does not penetrate into the building interior Therefore there is not expected to be any induction effects present on activities or materials within the interior of the building That is due to shielding by the building touch potentials will not be developed on metallic objects within the building
23 Railroads
231 Gorman Terminal Spur
The proposed railroad spur is located in located in transmission line segment 1 It leaves the CSX Hudson Line track running south for approximately 800 feet and then turns west eventually crossing the Segment 1 transmission line between Structures nos 4 and 5 and then enters the Gorman Terminal The crossing angle between the overhead transmission line and the railroad track is approximately SO degrees Due to the nearly perpendicular crossing both electrostatic and electromagnetic induction unto the track will be minimal
Alignment sheets for the track have been made available However track parameters are unavailable at the present time However in order to obtain an appreciation for the possible induced voltages and currents on the track a hypothetical example was simulated with the following assumed parameters
bull Single track approximately 2500 feet in length from the CSX main track to the end within the German Terminal
bull Track welded and electrically isolated from the main track
bull Rail weight of 132 lbyd
bull Ballast Resistance of 5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the Gorman Terminal
bull Rail to ground potential ~ 062 volts
bull Rail to rail open circuit potential = 19 microvolts
At the 345 kV 115 kV transmission line crossing
bull Rail to ground potential - 035 volts
bull Rail to rail difference potential = 760 microvolts
At the CSX Main Line
bull Rail to ground potential- 03] volt
bull Rail to rail open circuit potential = 175 microvolt
22
The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
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The maximum induced current in either rail is approximately 0]] mao In general the induced potentials are sufficiently low so that personnel hazard is not of concern If induction sensitive signaling circuitry is not added to the track the implementation of mitigation measures should not be necessary
232 Amtrak Railroad Crossing
The proposed 345 kY transmission line crosses an Amtrak railroad track ie the Post Road Branch line at approximately right angles east of New York State Route 9J Existing overhead signal and communication system conductors are subject to electrostatic induction effects The CSX railroad has the responsibility for maintaining these circuits
A request was made to CSX to provide data necessary for computer simulation of the interference environment CSX responded but possibly due to an error in communication information relative to a nearby track the Hudson Line was inadvertently provided It is our understanding that CSX is presently gathering the necessary data for the Post Road Branch line and will forward it to ESI In the interim the following hypothetical example has been analyzed to determine the approximate range of the rail induction levels that may be expected
A typical length signal block length of5000 feet has been ehosen for the simulation The signal block is assumed to extend from 1000 feet south of the crossing to 4000 feet north of the crossing The following additional rail parameters have been assumed
bull The rails are electrically continuous within the block
bull Rail weight of 132 Ibyd
bull Ballast Resistance of5000 ohmsKft
Both electrostatic and electromagnetic induction effects were taken into account in the computer simulation Computer simulation results are as follows
At the south end ofthe block
bull Rail to ground potential - 057 volts
bull Rail to rail open circuit potential = 201 microvolts
At the 345 kY transmission line crossing
bull Rail to ground potential - 065 volts
bull Rail to rail difference potential =0 414 microvolts
At the north end ofthe block
bull Rail to ground potential ~ 032 volt
bull Rail to rail open circuit potential = 90 microvolt
The maximum induced current in either rail is approximately 025 mo In general the induced potentials are sufficiently low so that personnel hazard is not of concern There are block signaling
23
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
systems that can function unimpaired in this environment However final judgment as to the need for mitigative measures in this situation must be reserved until signal equipment specifications are received and reviewed
24 Electrostatic Grounding Considerations
241 General
Proximity to an overhead HVAC transmission line results in voltages and currents induced on electrically conductive objects such as metallic structures fences etc By computer simulation two electrical parameters related to the induction levels can be calculated the structure developed open circuit voltage and short circuit current The open circuit voltage in the case of electrostatic induction can be extremely high for example in the thousands of volts The calculated short circuit current is generally in the range of milliamperes (rna)
The high voltage developed is not necessarily a safety hazard to personnel Upon contact to an energized object the high voltage results in an annoyance or startle condition However if contact to the charged object results in a eurrent flow to the person of 5 rna or greater a serious safety hazard is considered to exist The utility of the short circuit determination is that contact to the object cannot result in a magnitude of current flow to the person of more than the short circuit current Hence it can be readily determined if a hazardous condition exists If a safety hazard does exist ie a short circuit current of more than five rna grounding of the object must be considered Even when the short circuit current is less than the five rna safety criterion grounding of the object may be considered as the means to reduce the open circuit voltage to a level which is not annoying to personnel In this case the voltage of the object may be reduced to an imperceptible level even when the grounding resistance to earth is very large
When the short circuit current of the structure exceeds five rna the installed grounding system must have a resistance to remote earth which is much smaller than the minimum human body resistance of approximately 1000 ohms A person contacting the structure is electrically in parallel with the grounding system and a current division between the two OCcurs For example if the grounding system resistance was equal to 10 ohms and the body resistance equal to 1000 ohms approximately one percent of the short circuit current would pass through the person and 99 percent would flow into the grounding system
In sununary a grounding system is commonly employed even when the structure short circuit current is less than the five rna safety criterion This is done for (1) eliminating the annoyance factor due to the high voltage induced on the structure and (2) to provide a higher factor of safety for personnel
242 Grounding System Considerations
For a structure such as a fence or guard rail a grounding system to limit electrostatic effects is relatively easily specified since no other grounding system exists Grounding of a building 10
eliminate electrostatic induction effects is much more complicated because of the prior existence of grounding for the electrical power supply system for lightning protection etc The primary concern is that the new ancillary grounding system does not interfere with the functionality and effectiveness of
24
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
the existing systems Voltage differences and current loops between grounding systems must be avoided In addition the system must be designed so as to satisfy local electrical codes
Hence the electrostatic grounding system design is site specific ie depending upon pre-existing conditions relative to existing grounding systems structure design and so forth Hence the discussion here is limited to that of generic design approach which establishes the feasibility of achieving the necessary measure of safety
To eliminate safety hazards every metallic portion of the structure which is exposed 10 the external vertical electric field of the transmission line must be grounded This may require bonding of structure members as well as bonding to the grounding system A generic building electrostatic grounding system is outlined in Figure 27 The primary component is a insulated copper wire loop surrounding the building The loop may be installed at a distance from the building foundation of a few feet adjusting for local obstructions A 6 AWG wire buried at a depth of approximately 18middot inches is suitable Grounding is obtained by the installation of a number of vertical ground rods connected to the loop wire along the periphery For redundancy the minimum number of rods should be at least two The maximum number is determined by the required grounding resistance and the local soil resistivity As a general approach a grounding rod emplacement approximately every 30 feet along the wire loop periphery is suggested The rod should be standard eight foot length copperweld Similar considerations apply to the bonds between the wire loop and the structure Exact locations of the bonds are structure specific and have to be field detcnnined
243 Estimated Attainable Grounding Resistances
National Grid Garage Complex
Field measurements have indicated for a two-layer soil model an average upper layer soil resistivity of 35 ohm-meters with a thickness of approximately one meter The lower layer soil resistivity is equal to approximately 25 ohm-meters With this soil model the resistance of a single eight foot ground rod is approximately 12 ohms The resistance of five ground rods along the wire loop is estimated at approximately three ohms
Table 22 lists the building(s) short circuit currents as approximately 15 rna which would be the body current without the grounding system installed After installation of the grounding system the maximum body current assuming a worst-case body resistance of 1000 ohms the body current is limited to (153)11000 ~ 45 microampere
Yonde Farms Comolex
The measured soil resistivity indicates an upper soil resistivity on the order of 732 ohm-m with a layer thickness of 153 meters and a lower layer resistivity of 121 ohm-meters The estimated ground rod resistance is approximately 100 ohms Six ground rods placed around a building perimeter results in a grounding system resistance of approximately 20 ohms Table 21 indicates that building 4 has the highest short circuit current of 47 rna With the recommended grounding system emplaced the maximum body current is limited to (47middot20)(1000+20) = 92 microamperes
In general the emplacement of the recommended generic grounding system will result in a considerable safety margin being achieved
25
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Note Bonding between conducting structure members and the insulated connecting wire to be made at appropriate locations as determined by field inspection
bull
INSUIJTED CONNECTING WIRE BURIED 18 OR AT GREATER DEPTH VERTICAL
GRDUNDING RODS SPACED AT 30~
IJlITERVALSAROUND PERIMETER
FIGURE 27 GENERIC GROUNDING SYSTEM
26
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
30 Electromagnetic Induction
The 345 kV transmission line does not run parallel to any long buried conductors in Segment 2 In Segment 3 however the transmission line will parallel a Dominion 12~inch natural gas pipeline throughout the segment and a fiber optic cable from approximately Interstate 1-90 to the Reynolds Rd Substation The fiber optic cable is non-conductive and hence will not be affected by electromagnetic induction In Segment 2A the Dominion 12-inch pipeline parallels overhead 115 kV transmission lines from structure T-57A to Greenbush Substation where it leaves the right-of-way
Electromagnetic induction for both steady state and fault conditions must be addressed Since there are other transmission lines on the right-of-way the voltage induction on the pipeline for steady state operation is dependent upon the magnetic fields generated by all of the circuits Hence the computer simulation sums the induced voltage contributions from all operational circuits in Segments 2A connector 2A and 3 For fault conditions however the induced pipe voltage and current in Segment 3 are determined taking into account only the impact of a fault on the 345 kV transmission line In Segment 2A faults on the closest structures (carrying circuits 17 and 4) to the pipeline are evaluated In Segment 2A Connector a fault on structure T-66 is evaluated relative to pipe induction effects
31 Steady State Induction
311 Pipe Voltage
Voltage profiles for the Dominion pipeline are plotted in Figure 31 assuming that only the existing 115 kV transmission Jines are present which is representative of the present configuration The pipeline voltage is above the NACE (National Association of Corrosion Engineers International) personnel safety criterion of 15 volts over the pipeline collocation which runs in Segment 2A from the Greenbush Substation to Structure T-57A and in Segment 3 from Structure 35 to the Reynolds Rd Substation Voltage profiles are plotted for the conditions where (I) all circuits are carrying balanced load (phase) currents and (2) where the circuit load currents are randomly unbalanced by up two percent Unbalanced conditions which may be reached occasionally result in higher voltage induction levels and must be considered when establishing mitigation system requirements
Figure 32 is a plot of the induced voltages assuming that the proposed 345 kV transmission line is operational in Segment 3 The pipeline voltages are increased by approximately 50 percent Although the pipe voltages are increased with the addition of the 345 kV transmission line comparison of the moo figures shows that noncompliance relative to the NACE safety criterion is a pre-existing condition Figures 31 and 32 are a result of computer simulations which have assumed the pipeline to be unmitigated
For an existing pipeline a retrofit mitigation system consisting of vertical anodes is generally preferred due to ease of installation However a computer simulated trial mitigation system using a vertical anode configuration has shown that for this right-of-way many one (1) ohm resistance anode grounds would be necessary To achieve such low resistances anodes with lengths of 300 to 400 feet would be required Soil resistivity measurements available to date indicate that the feasibility of obtaining suitable grounding sites in the number required is questionable Hence this approach was terminated
27
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Fig 31 Steady State Pipe Induction wlo 345 kV Transmission Line
120
bull ~ gt
80 ~ C S 0 n
v
an40
No Pipe Mitigation
~ r-- shy
2 UnbalancedT-une
Load Currents
-
~
BalanltEdr-une
Lo~ Ctrrents
lSlart
Segmerc IlIJ
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 32 Steady State Pipe Induction with 345 kV Transmission Line No Pipe Mitigation
200
150 ~
2 U~d T -- shy
~-7 gt
~
~ 100
c o
ltgt n
~~
I
aaiarcsc Tune Load CuTef1IS
50
~ 0
Segment 2A
nreercus-Substation
Slan Segmenlll3
Reynolds
Substahm J 0 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
28
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
A more electrically efficient grounding system for the pipeline is obtained by the use of horizontally buried bare conductors placed parallel to the pipeline Typical installations are either standard size zinc ribbon or copper conductor eg no2 AWG wire The wire is placed at a depth of at least 18shyinches and approximately three feet to the side of the pipe Placing the conductor on the 345 kV transmission line side of the pipeline is generally more preferable but not absolutely necessary on this right-of-way To achieve the required grounding it is necessary to bond the wire to the pipe at periodic intervals The distance between successive pipe bonds is not critical in the present application because the primary source electromagnetic coupling to the pipeline is inductive rather than conductive Hence spacing on the order of one-half mile or less is acceptable If a copper wire is used as the grounding element isolators such as the Dairyland Electrical Industries PCR (Polarization Cell Replacement) units must be inserted in the bond leads in order to provide electrical isolation between the copper conductor and the pipeline cathodic protection system
To mitigate steady state induction in the Segment 2A and Segment 3 collocations two mitigation wire segments originating and ending in the Niagara MOhawk transmission line right-of-way have been found to be optimum in the sense that adding additional wire between the two segments does not result in an increase in mitigation The first wire segment is approximately 6600 feet in length running from the Greenbush Substation to structure 39 in Segment 3 The second is approximately 2400 feet in length running from structure 64 to Reynolds Rd Substation Bonds from the mitigation wires to the pipeline should be made at the beginning and end of each wire segment and at approximately the mid-point of the first mitigation wire If desired additional bonds such at existing pipeline test stations may be installed Where the mitigation wire crosses roadways it may be interrupted (cut) when necessary In such locations the wire must be bonded to the pipeline on each side of the cut For example it appears that mitigation wires cross three main roads bull ie Old Mill Red Mill and NY State Hwy 4
An alternative mitigation system using a horizontal buried conductor as a shielding element rather than a grounding element is occasionally used for convenience because bonding to the pipeline is not necessary To achieve the necessary degree of shielding the wire must be long and continuous eg extending from Greenbush Substation to Reynolds Road Substation Such an installation would be more costly but the defining factor in not using this approach is that the cuts made at road crossings or other obstructions would severely degrade the shielding effectiveness
Emplacement of the horizontal bonded to the pipeline mitigation conductors does not result in a reduction in pipe voltages to the NACE criterion over the complete lengths of Segment no 2 and Segment no 3 This is shown in the Figure 33a plots The consequence of this shortcoming is that gradient control mats must be installed at pipeline test stations and at all above ground pipe appurtenances at locations where the NACE criterion is exceeded
The mitigated pipe voltage is plotted in Figure 33b under the assumption that the 345 kV transmission line is out of service It is interesting to note that the pipe voltages are not significantly different from those plotted in Figure 33a It may be deduced therefore that if the pipeline were mitigated for the existing transmission lines the addition of the proposed 343 kV transmission line would not have a significant impact upon the resulting pipe voltage
It should be noted that the plots in Figures 33a and 33b are theoretical and based upon ideal conditions eg eaeh transmission line operating at its normal loading A change in the loading of any one line will affect the pipeline voltage profile Henee the final determination of the mitigation system effectiveness must be made through pipe voltage measurements made in the field over a period of time In some Cases adjustments to the originally proposed mitigation design may be necessary to obtain the desired results
29
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
__
10
Fig 33a Steady State Pipe Induction with 345 kV Transmission Line
40
30
With Segmented Horizontal Wire Mitigation
2 Unbalanlted T-Line
load Currents ~ r
J~ y~ ~~~ ~~Segmenlll2A (Start
Genbush lSe9fT1erll l3
Reynold Rd
Substation Subsatoo------------------c-o o 5000 10000 15000 20000 25000
Distance trom Greenbush Substation - ft
Fig 33b Steady State Pipe Induction wo 345 kV Transmission Line With Segmented Horizontal Wire Mitigation _
40
Greenbusn
10
soosauon __--o o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
ZYo Unbalancedr-u-e
Load Curren(s r---shy
) t-
~~T ~ Loa] Currents
ReynoldsRd
--__---- - ---501gt__00__
30
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
312 induced Pipe Current
The induced pipe currents are plotted in Figures 34a and 3Ab The Figures indicate respectively the induced pipe eurrents for the 345 kV transmission line operational and out of service The staircase appearance of the pipeline profiles are due to current drainage through the bond wires
Figure 35 plots the induced pipe current for the present state of the collocation ie the 345 kV transmission line is absent and the pipeline is not mitigated The induced pipe current is much lower than for the previous scenarios However this does not necessarily imply that the ac current density leaving the pipe is reduced and hence the pipe corrosion rate is less The current density leaving the pipe is proportional to the rate of change of the pipe current with distance that is to the slope of the pipe current profile Comparison of the Figures 34 and 35 plots shows that the slope of the pipe current profile in Figure 35 is much larger than for any of the plots in Figures 4a or 4b Hence when mitigation is applied to the pipeline the pipe current is increased but the pipe current density through the pipe coating is decreased because of the current leaves the pipe through the bond wire connections rather than through the coating holidays The implication is that ac pipe corrosion is reduced
Fig 34a Induced Pipe Current with 345 kV Transmission line lMittl Segmellf8d WQ~iZQlltdll li~8 MitigdltiQII
120
c 80 shyE ro
~ Balanced TmiddotLIle
Load Ccrents 0 cgt w O 0 40
Bond ~l _ comec1lon~
Segment2A 1Start Segment 3 o Greenbu91 Rejnolds Rd
Substation SlbslaIOIl
o 5000 10000 15000 20000 25000 Distance from Greenbush Substation - ft
31
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
25
Fig 34b Induced Pipe Current wlo 345 kV Transmission Line
80
60
20
Omiddot
Wilh Segmented Horizontal
2 Unbalanced r-u-e I Loadcutents ~j
r___-J ~r------- ~
-~~
Segmenl fl2A
Greenbutl
sccseucn
0
Boo ComectJOo
i5 13rt
secrrere 3
5000 10000 15000
l I
Boo correcacos ~
RelloldsRd J Substatlon
20000 25000 Distance from Greenbush Substation - ft
Fig 35 Induced Pipe Current wlo 345 kV Transmission Line Without Pipe Mitigation
40
35
gtSegment 2A tStart
Segmert 3
SubstalJon
BalancedT-lme
~~ ReoldsRd
Scostatcn
o 5000 10000 15000 20000 25000 Distance from Greenbush SUbstation - ft
32
20
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
32 Fault Current Induction
321 345 kV Transmission Line Faults in Segment 3
The voltages and currents induced on the pipeline are dependent upon the particular transmission line structure faulted Hence it is necessary to simulate faults at several structures along the common right-of-way in order to obtain a reasonably complete representation of the induction levels Induced pipe coating voltage profiles after mitigation with the segmented horizontal wires are plotted in Figure 36 for simulated faults at structures nos 28 35 42 49 56 63 and 68 The profiles include induced voltage contributions from both the magnetic fields produced by the currents in the overhead conductors and the potentials developed along the pipe from soil conducted currents injected at the faulted and adjacent structures
It is desirable to limit the voltage developed across the pipe coating to 3000 volts or less Generally at this voltage level pipe coating puncture will not occur and ionized regions (arcs) developed at existing holidays will be small enough to preclude significant pipe wall damage of any significance The plotted profiles indicate that the voltages developed across the pipe coating are not excessive
Fig 36345 kV Fault Induced Pipe Coating Potential Superposed Potential Profiles for Faults at TW1S 28 35 42 49 5663 and 68
Pipeline Mitigated
~ 1200 o gt
rn e o () lt1) 800shyc Q
bullbulle o m roE 400
o Q
o Pipelile Enters
345 ky Right-oj-Way ------ __-r-rshy
40000o 10000 20000 30000 345 kV ROW Station - feet
The fault induced pipe touch and step potentials are plotted in Figures 37 and 38 respectively
33
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Fig 37 345 kV Fault Induced Pipe Touch Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 495663 and 6~
Pipeline Horizontal Wire Mitigated
~ 1200
~
2 a c
g 800 3 0 if)
1l ANSIIIEEE Sid 50 rntenql 3 400
8bullac
o Reynolds Rd Empire Plpelne En~
Gene-anon Plant 345 kV Rpoundlht-01-Way SubstalIOO
o 10000 20000 30000 40000 345 kV ROW Station - feet
Touch potentials between the pipe or a pipe appurtenance and the local soil must be limited for personnel safety Guidelines for determining safe potentials are given in ANSIIEEE Std80 The limiting safe potential as determined from the Standard is plotted in Figure 37 along with the calculated touch potentials In general the potentials exceed the safe value and gradient control mats are required in Segment 3 at pipe test stations and above ground appurtenances However calculated step potentials plotted in Figure 38 are well below the ANSIlEEE Std 80 requirement
The currents induced in the pipe by a fault at each of the subject structures are plotted in Figure 39
34
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Fig 38345 kV Fault Induced Pipe Step Potential Superposed Potential Profiles for Faults at Twrs 28 35 42 49 56 63 and 68
Pipeline Ho~ontal Wire Mitigated
150 J o gt ID
0shyltL
ID 100 gt o
~ c E it2 50
o EmpH~
aeneacon Plant
o 10000 20000 30000 345 kV ROW Stalion - fee
40000
Fig 39 345 kV Fault Induced Pipe Current
Prpeljie Enters
345 kY Rlghlof-Way
Superposed Current Profiles for Faults at Twrs 28 35 4249 56 63 r--shy
Pipeline Horizontal Wire Mitigated I IL-------middot--middot
~
bullEc 800
C ID t 0 U ID 0shy 400 ltL
o Empire Plpelrle tntes
345 kV Right-oPNay Generallon Planl
o 10000 20000 30000 40000 345 kv ROW Station - feel
35
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
322 115 kV Transmission Line Faults in Segment 2A
Pipe coating potentials after the pipeline is mitigated are plotted in Figure 310 for computer simulated faults at structures T-61 T-59 T-57-A and T-66 Along the right-of-way the potentials are sufficiently low so that pipe coating or pipe wall damage would not be expected The only exception is across from Greenbush Substation as the pipeline leaves the NMPC right-of-way In this region relatively potentials are calculated which are in excess of the desired 3000 volt criterion These potentials have been calculated assuming a substation grid ground potential rise of 15000 volts which is on the conservatively high side Data for the actual station GPR have not been received When the data are provided if they differ significantly from the assumed value pipe potentials will be recalculated If the pipe coating voltages still remain above the criterion a Faraday Cage shield can be implemented between the substation grid and the pipeline
The pipe touch potential is plotted in Figure 311 The potentials exceed the ANSIlEEE safety criterion over most of the right-of-way Hence gradient control mats will be required at any location where the pipe or a pipe appurtenance can be contacted by personnel Zinc ribbon is the conductor of choice for the mats which should have a minimum diameter of six feet Typical burial depths are at one to one and one-half feet For redundancy at least two connections should be made between the mat conductor and the pipe appurtenance It is also recommended that a four-inch overlay of washed crushed stone be placed over the mats with the top of the stone layer flush with the ground To reduce step potentials in the vicinity of the mat the gravel should extend outward to a distance of approximately four feet beyond the periphery of any malar grounding system The gravel overlay provides an additional measure of safety by increasing the tolerable touch potential to approximately 5500 volts An acceptable conductor is the standard size zinc ribbon manufactured by Platt Bros
Figure 312 is a plot of the step potential above the pipe It is well within the limits determined from the ANSIIEEE Standard amp0 The pipe current profiles are plotted in Figure 313
36
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Fig 310 Segment 2A Fault Induced Pipe Coating Potential u er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
Pipeline Horizontal WJre Mitigated
4000
~
E 3000 rn a obulla o
~ 2000
~ ~ o 1000 a
o Greenbush Re~dsRd
Substaton SUbsta~on
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 311 Segment 2A Fault Induced Pipe Touch Potential Su er osed Potential Profiles for Faults at Twrs T-61 T-59 T-57A and T-66
6000 Pipeline Horizol1lal Wire Mitigated
5000
0 ~ 4000
~ ]fi 3000 L s a ~ 2000 o
a
1000
o Substation SubsatrcJrl
o 5000 10000 15000 20000 25000
Distance from Greenbush Substatton ft
37
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
3000
~ 2000 a
~ sect
i c 1000 o
o
Fig 312 Segment 2A Fault Induced Pipe Step Potential Su er sed Potential Profiles for Faults at Twrs T61 T-59 T-57A and T-66
Pipelinp Horizontal Wire Mitigated
ANSIIEEE se BOceaeneo
Segment 2A Slart
5egmentllJ
j ~
A
JjIJ ~JiNv~ Greenbush
Substation
Reynolds Rd
Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - ft
Fig 313 Segment 2A Fault Induced Pipe Current u osed Current Profiles for Faults at Twrs T-61 T-59 T-57A and Tc-66-_
Pipeline Horizontal Wire Mitigated
2500
bull E-2000bull
-~ I J=shy-1-JI b =-==-=--
Segmenl 2A 1Slart SegmenlJ
Greenbush Reynolds Rd
Substation Substation
o 5000 10000 15000 20000 25000
Distance from Greenbush Substation - tt
38
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
40 Summary and Conclusions
41 Summary
The Reynolds Road - Empire Generating Co 5 circuit 345 kV transmission interconnection has been studied to determine the extent of electromagnetic compatibility problems with other facilities located on or near the right-of-way Computer simulations of the electromagnetic interference environment produced by the transmission line were made to determine steady state and fault induced voltage levels at collocated facilities Based on these simulations a mitigation system design approach has been evolved to minimize induced voltage hazards to these facilities In addition the induction effects produced by the reconfiguring of several 115 kv transmission line circuits in Segment 2A have been assessed
Electromagnetic compatibility concerns have been addressed for the following 345 kV transmission line segments
bull Segment 2
bull A gun shoplbarber shop complex adjacent to the right-of-way which could have been subject to electrostatic field induction effects By visual examination of the building complex it has been determined that the building materials are none conductive having an asphalt roof and being of brick construction Hence the transmission line electric field does not penetrate into the building interior and electrostatic induction is not a problem relative to interior activities
bull Electrostatic induction to numerous metallic fences and guard rails located at road crossings which are situated at various angles relative to the 345 kV transmission line By computer simulation a universal model has been developed which provides open circuit voltage and short circuit estimates for the scenarios encountered along the right-of-way It has been found in general that short circuit currents developed on these facilities are below the NESC safety limit of 5 rna Grounding of these structures provides adequate protection for personnel
bull An initial electromagnetic compatibility analysis was completed for an Amtrak Railroad Crossing near Structure 20 The results of computer simulations indicate that track induced voltages are very low thus raising the possibility that induction problems may not be severe However a final determination of electromagnetic compatibility with the block signaling system cannot be determined until system specifications are received and reviewed
bull Segment 3
bull Electrostatic induction to metallic fences and guard rails The above Segment 2 study extended
bull Electrostatic induction to the National Grid Garage and the Yonder Farms building complexes Both facilities were found to be subject to high open circuit potentials High short circuit current capacity was found to be likely on several Yonder Farm buildings which is a concern relative to personnel
39
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
safety Concepts for grounding of these facilities have been presented which remove the electrostatic induction issues
bull Electromagnetic induction to a natural gas pipeline and a fiber optic cable The cable is non-conductive and therefore is not subject to electromagnetic interference effects Relative to the pipeline it was found that steady state induced voltages exceeded the industry accepted safe value of 15 volts A grounding approach consisting of two segmented conductors buried adjacent to and periodically bonded to the pipeline supplemented with gradient control mats installed at above ground appurtenances was found 10 provide adequate personnel and pipe mitigation for both steady state and fault conditions
bull Segment Connector 2A
bull Review of the alignments in this segment has not revealed any collocated facilities that would be subject to electromagnetic interference
bull Segment 2A
bull The Dominion Pipeline extends into this segment leaving the Niagara Mohawk right-of-way at the Greenbush Substation The proposed segmented wire mitigation system with added gradient control mats at above ground appurtenances limits steady state and fault induced voltages to safe values along the segment except for the pipeline departure at Greenbush Substation It was found that a larger than desired voltage eould be impressed on the pipeline due to the ground potential rise of the Greenbush Substation grid Additional mitigation at this location may be necessary ie installation ofa faraday Cage shield at pipeline
42 Conclusions
Electrostatic and electromagnetic compatibility issues raised by the construction of the proposed 345 kV transmission line have been addressed A number of facilities located on or adjacent to the transmission line right-of-way have been identified as being subject to electrical induction effects These have been modeled by computer simulation to determine the level of mitigation required For each facility where palliative measures were found to be necessary an adequate conceptual mitigation approach was found to be available Hence it is concluded that with the recommended mitigative measures emplaced the electromagnetic environment produced by the transmission line can be sufficiently managed so that the safety ofpersonnel and the integrity of collocated facilities are not compromised
40
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Appendix A
Two Layer Soil Resistivity Models
41
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Two Layer ModelTower21 (East - West)
layer Depth - elers ~f
layer 1 oraquo 4302 lsyer2 (gtO 150B
CDmp~ted Model_~l3ye~bull ~
Rcsis
CompUlell MollI-la)er 2
10000~I~----------c7-------_L-7~----------~L 100 1000
Wenner Measuremenl Pin Spacing - meters
Two Layer Model Tower I- 21 (North - South)
n Ii ~
1000 La)er Depth - meters f
layer (gt~ 5i2J layer 2 eraquo J5fi s
til = 0545
1~_~ITl~utd Model - La)~~~_1_App
~-I
bull
I i
i l
Compuled Mdel _ Layer 2
n100 01 1 i
100 1000
Wenner MeaslJrlment Pin Spacing - meters
42
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
1000
Two Layer Model Tovrer I 25 (East - West I
Layer Depth - meters
10000 i)ii~
Computell Mollel - Layer bull 1
Layer1 r = 831 8 th = 0258
Layer2 r 154 I App
10 100 1000
Wenner Measurement Pin Spacing shy meters
Two Layer Model Tovrer I 25 (North shy South)
10000r~middot~-_-_-
Layer Depth - meten ~---_-
I~---_-
~ ~-
App
Resls
Layer I p= 1678 Ul = 1-0 layer2 r = Y75
Computed Model - laye
~
~ CumptedModel-laye~2
100 Orl--------------------~--~--~-----I~ODD10 100 Wenner Measurement Pin Spacing - meters
43
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58
Two Layer Model Tower t 49 I East - West)
layer Oepth - meters
Aopmiddot
Lgtye1 (gt 42 6 LaYltl 2 r 2amp 6
th
Computed Model -layer 1
126
Computed Uodel - layer 2
R~si
100---~-~~-~~~7--~--~---~-~~--~-~--~~~-C10ll1I100
Wenner Measuremenl Pin Spacing - meters
TWDLayer Model Tower t 49 (North - South J
laye Oepth - mtrs
( co 100
( )
layer 0
layer 0
as bull
~ 0 01132
Aop
__(_ll1J_Il_~d__~~~_~_~~il)--_~ __1__ _
Cumpuled Uudel Laybullbull
R~is
10 111 100 umu
Wenner Measurement Pin Spacing - meters
44
Two Layer Model Tower 54 (East - West)
layer Depth - melers if I1000
~
0Lyer1 0 az a ttl Layer 2 1 as s
App
CDmp-LI~ Model - layer
__l2~~t~_d __t4_Ddel - ~Y~~~~
i
Rtsis
I 100
10 100 1000 Wenner Measuremenl Pin SpacinJ - meters
T~ Layer Model Tower 54 (North - Soulh)
layer Deplh - melers
Layer 11= 322 11=99 I
layer 2 I = 1558 Ap
Con-pIted Model - Lrer~ 2
1000
CDmputed Model - Layer
100 ~O--------~---------(o-~----~--i100 10000
Wenner Measuremenl Pio Spacjnq - meters
45
1000
Two Layer Model Tower 59 (East - West) Layer Depth - meters
a
la)1(J=21011 layer2(J=399
App CDmputed MOdel - layer 1
11l1111
Compu~ed Mod1_ Layr 6 2
Wenner Measuremenl Pin Spacing - meters
TWIl layer Model Tower 59 (North - South) lay Depth - eters
101100fPf2--_- ~~~-----------__--
19ye6(J=1~O th=0632 layer6gt(J=29S
App
Compuled Model - layer 6 1
nests ---~~_-J Computed de - layer 6 gt
Wenner Measurement Pin Spacing - meters
46
Two layer Model Tower B3 ((ast - West)
liyer Deptn melers
10000 ~-i==========t---------~--e------------l layer l~ IU91 layer 2 ~= 24S11
lllputed Mo~el - layer
Computed Model - Layer 2
nests
1000 O~-------~--___---------_----------__10 100 1000
Wenner MeasuJl~menl Pin Spacing - meters
Two layer MOdel Tower 63 (North - SDJh I
llyer nepth - meters
100000 r(~~===========-------------layer laye 2
~=3514
~= 3112 4
th = on
App
10000
Compute~ PIIodel-laye
Resis
Computed MOdel - layer 2
Wenner Measurement Pin Spacing - meters
47
TWlJ Layer Model Tower 61 (Easl- Wesl)
100lIfri---~--
layer D~pth - mete
~~----_-_- c---_shy__~ l
-------------
Ll lOye r l r= ImiddotHl
uyer 2 r= 38 3 Ih =0 045
ApI
Computed Mod~1 - lay~r II- 1
1000
ne sts
100 ~--~--~~--~-----~-----~t------~--~~1 100 1000
Wenner Measurement Pin Spacing - meters
TWlJ layer Model Tower 61 I North - South)
layer Depth - meters
1000 rr~middot------middot~--_-=============-----------l
Computed Model - layr 1 layer II 1 P = 822 Layer1l2p=o318
th=oOZY3
Computed Model shy layer 2
R~sis
100 1----~--_l~T------~-~-~---------~_it 100 1000
Wenner Measuremenl Pin Spaclng- meters
48
Two layer Model Tower 70 (North - South)
10000 (rLj~c--~-~-----------~------------------~l
App
ComplllU lIlodel - layer 2
layer p= 132 15 layer2p=12L1
1000
Hests
100 oicl---~-----i---~---------------~~-oi10 100 1000
Wenner MeasuremEnt Pin Spaclnq - meters
Two Layer Model Tawer 30 (Easl- West)
La Dept - meres
l a)e bullbull 1 rgt = 30 6 ttl = 1 II I lltl)e bullbull 2 rgt = 461
I
Computed MOdel - lityer bull 1
Resis
teau
Wenner Measurement Pin spacsnq- meters
49
I
Two layer Model TlJWer 30 (North - South) Layer Depth _ mltters
i-shy snIJ HlUO
LOlyerW1fgt302 th= 3 9 1
LilyerW 2 fgt= 423
App
Compllled Model ~ Laye W2
Compuleo Model-_Laye WI
nests
100 O~--~----------~-----------------~10 100 1000
Wenner Measurement PIn Spacing - meters
Two layer Model TDYVer 37 (North - South)
10000~============-------~----------------l Lay fgt= no II
I Laye ~ fgt 1D~ II
~mputed Madel - Laye 1
10011
Aesis
100 O~l-------------~-~~~~-- --~------~e10 100 1000
Wenner Measuremenl Pin Spacing - meters
50
1000
Two laylf Model Tower 37 (East - West)
Layer Depth - eter
10000 [~~ilt==========~------------------------4
PO Computed Model - layer 1
-- Computed Model - layer Z 1000
10 U~-------------~-------_---------~100 1000 Wenner Measurement Pin Spacing - meters
Two layer Model Tower 42 (East -west)
layer Depth - meters lDDDIlr-----------------------~___-- c
lilye1p=63 111=53 lilyer 2 p= Hi2 Y
ppp
Computed odel _ l~yel 2
Compured Model - layer 1
nests
I 100 1000
Wenner Me~surement Pin Spacing - meters
51
1000
Two layer Model Tower I 42 (North - Soulh)
lilye Depth - meter n I
1000 iU5
layer I f 56 7 tiJer2 f= 764 Cgmputed Mgde - taye 2=3~---
compute bullbull~ y ~ App
I
Resls
101l )--~~-~--o------_L-c----~---~ 100 1000
Wenner Measurement Pin Spacmg - meters
Twu layer Model 0 Tower 143 I East - west I tIY~ Depth - ters
10000 ~r- ~ ~J c_C__-------~--_-----
Cgmputd Mmlel - laye
Wenner MeaSUlement Pin Spacing - meters
52
Two layer Model Tower 43 (North - Soulh I
Layer Depth - meters
10000 rmiddotmiddotfj------------------~--------cc_--------------~
Layer 1 1 154 Layer 1 1 213I
App
Computed Model - tOJye II 1
100[1
Wenner Measurement Pin Spacing - meters
Two layer Model Tower 47 I East - Wesl)
layer Depth - meters
1000 i-----------------------~------------_C
layer I 1 4lo1 lh 12 Layer II 2 1 Igt
App
Computed Model - uye II I
C~_IllP_lIte_~_Moder__- L_ay~r 11_2
10[1 O~--~-~-~~~~T--~---~---~-------~~-~~~~~10 100 1000
Wenner Measurement Pin Spaciflg - meters
53
10011
Two Layer Model Tower 11 47 I North - South)
layer Depth _ meters n
1000 fl)~~==========~-~~~-~-----------------4
COmPUI~IJ MOIJel - layer
nests
Compul~IJ Mud - layer 2
100 0~1-~~~-------~_-~__L_e-- ------ui1 100 1000
Wenner Measurement Pin Spadng - meters
TWO Layer MDdel Tower 11 T51A (East - Wfsl J
layer Depth - meters 10000 cLe-- --_-_-_~ L-- ~ ~
r_~o_~~ted MO~I -_l~e
+ Compuled Mollol - layer 2
Resis layer p e 6974 U1 18 layer 2 f 972
Wenner Measurement Pin Spacing - meters
54
TWll Layer Model Tower II- T51A (North - South)
lay~ Depth - meters 100000 I) n lt ~u H
lay~r 1 1 U8S6 Lay~r - 1 2348
lh S1 1
App
Computed Mod1 - Ulyer - 1
10000
Resis ~~_~~__-+ Computed Mollel-l3yer 2
100OO~I~----------~-------------------------100 1000
wenner Measurement Pin Spacing - meters
TWll layer MDdel Tower I T59 (East - West)
l~ye 1 1 11113 ~ layerampr-21=1S9S -~I
Computed Mollel - lay I-- _----_-shy100110
Wenner Measur~mentPin Spacing - meters
55
MDdel Tower bull T59 (North - South 1 Two layer Ih _ meters n
Layer Dep
App
Compute d Model - layer 2
llT- 1161 ( east - Wesl) ~~ d Two layer f4 Oplh _ metergt - -_layet
TOOOOO~ ~o _
layer1~HQ Uyef2-
App
Computed Modelmiddot lay 1
10000
lt
Reds
cornpuled Model _layer2J
1001) 01 100 1000
10 t Pin SpaclOQ _ metersWenner Measuremen
56
Two layer Model Tower T81 (North - South)
Layer Depth - metelS
Computed Model - layer 2
nests Layerl [gt=9014 111=11 layer 2 [gt= 250 5
10000~1----------c--_L_------c---~--------~10 100 1000
Wenner Measurement Pin Spuing - meters
Two Layer Model Tower 69 I North - South) layer Depth - meters
10000 FlL~===========~------------------------_LlII layer 1 1= 555 ~ I layer 2 1= 212
App ComplJted Model - layer 1
Computed Model - layer 2
nests
10 10
Wenner Measurement Pin Spacing - meters
57
1000
1000
Two Layer Model Tower tJ B9 LEast - West)
lyer ueprn - meters
Computed Model - Layer I
App
- Computed Model - lyer 2
Resis
uyel r-- 533_3 tll=Z] layerz r-= 06 4
1000~l----~----------~-_c_-~-----------I IOl 1000
Wenner MeltlslJremenl Pin Spltlcing - meters
58