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NESC Subcommittee 5Changes to the 2017 NESC
Joseph Rempe
18 October 2016
Re-format Rule 241.C. At Crossings
2
241. Application of grades of construction to different situations
2012version
Re-format Rule 241.C. At Crossings
3
241. Application of grades of construction to different situations
2012version
2017version
Re-format Rule 241.C. At Crossings
4
241. Application of grades of construction to different situations
2012version
2017version
SameWords
EasiertoComprehend
Grade N
5
CPIntention:
ChangeGradeNEmergency&Temp
EliminateGradeNfromTable242-1
Grade N
6
CPIntention:
ChangeGradeNEmergency&Temp
EliminateGradeNfromTable242-1
FinalModification:
KeepGradeN
AddNOTE toRule240.A.General:NOTE: For emergency or temporary installations,
see Rule 014.
Grade Cx
7
CPIntention:MakeGrade“Catcrossings”anofficialGrade:Callit“Cx”
ListinSection24-GradesofConstruction
Grade Cx
8
CPIntention:MakeGrade“Catcrossings”anofficialGrade:Callit“Cx”
ListinSection24-GradesofConstruction
PotentialModification:EliminateGrade“Catcrossings”
Grade Cx
9
CPIntention:MakeGrade“Catcrossings”anofficialGrade:Callit“Cx”
ListinSection24-GradesofConstruction
PotentialModification:EliminateGrade“Catcrossings”
FinalAction:Rejectanychange
Revise Table 242-1Grades of Construction Applications
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Revise Table 242-1Grades of Construction Applications
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CPIntention:Improvelogicallayoutandformat
Columnssequencefromlowtohighvoltage
Rowssequencefromlowtohighvoltage
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2012Table242-1
13
2012Table242-1
14
2017 Table242-1
15
2017 Table242-1
Revise Table 242-1Grades of Construction Applications
16
CPIntention:Improvelogicallayoutandformat
Columnssequencefromlowtohighvoltage
Rowssequencefromlowtohighvoltage
FN3reversed;highergradeinthetable
3 Grade B C construction shall may be used if the supply circuits will not be promptly de-energized, both initially and following subsequent breaker operations, in the event of a contact with lower supply conductors or other grounded objects.
Revise Table 242-1Grades of Construction Applications
17
CPIntention:Improvelogicallayoutandformat
Columnssequencefromlowtohighvoltage
Rowssequencefromlowtohighvoltage
FN3reversed;highergradeinthetable
AddFN11– GradeNfordielectricfiber-opticsupplycables
Revise Table 242-1Grades of Construction Applications
18
CPIntention:Improvelogicallayoutandformat
Columnssequencefromlowtohighvoltage
Rowssequencefromlowtohighvoltage
FN3reversed;highergradeinthetable
AddFN11– GradeNfordielectricfiber-opticsupplycables
Meet Rule 230F1b – Insulated Comm Cables in Supply Space
andSupported by effectively grounded messenger
orBonded at intervals specified in Rule 092C to Supply messengers supporting cable meeting Rule 230C1
Revise Table 242-1Grades of Construction Applications
19
CPIntention:Improvelogicallayoutandformat
Columnssequencefromlowtohighvoltage
Rowssequencefromlowtohighvoltage
FN3reversed;highergradeinthetable
AddFN11– GradeNfordielectricfiber-opticsupplycables
FinalAction:Accept
k-factor
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Introducedin1941§DistrictLoadswerereduced
Clearancesbasedonprevioushigherloads
K-factorapproximatedthesameresultantloadingonthewiretocreatethesamesags§Clearancesbasedonsags,nottension
Resultingincreaseintensionnotintendedforstructuraldesign
2007NESCaddedDistrictLoadMaptoSec23
k-factor
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CPIntention: Setk=0insection25
Onlyaffectsguyedstructures
Iftensionssetat%limit,designtensionsincrease -everydaytensionsincrease
Affectonstructuresconsideredsmall
k-factor
22
CPIntention: Setk=0insection25
Onlyaffectsguyedstructures
Iftensionssetat%limit,designtensionsincrease -everydaytensionsincrease
Affectonstructuresconsideredsmall
FinalAction:Reject
WillcoordinateeffortwithSC4innextcycle
Delete Rule 243.C.4
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Delete Rule 243.C.4
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When communication conductors are required tomeet Grade B or C, only the requirements formechanical strength for these grades are required.
Delete Rule 243.C.4
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Delete Rule 243.C.4
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Two new grades of construction:Undefined Loads + Grade B StrengthUndefined Loads + Grade C Strength
Delete Rule 243.C.4
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FinalAction:Accept
Rule 250C: Add Wind Return Period
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Rule 250C: Add Wind Return Period
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NOTE: The commentary to ASCE 7-2005 indicates thatthese wind speeds represent a 50-to-90 year meanrecurrence interval.
Rule 250C: Add Wind Return Period
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NOTE: The commentary to ASCE 7-2005 indicates thatthese wind speeds represent a 50-to-90 year meanrecurrence interval.
FinalAction:Accept
Rule 250C: Eliminate 60 ft Exclusion
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Rule 250C: Eliminate 60 ft Exclusion
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Forgeeht aboutit!!!!
Non-linear analysis
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CPIntention:
Rule250BGradeB IncreaseStrengthFactorwhenusenon-linear
Rule250BGradeC DecreaseStrengthFactorwhenuselinear
Rule250C&D .75to.79
Non-linear analysis
34
Non-linear analysis
35
Intention:Rule250BGradeB IncreaseStrengthFactor
whenusenon-linear
Rule250BGradeC DecreaseStrengthFactorwhenuselinear
Rule250C&D .75to.79
AsModifiedin2013:Rule250B ReduceLFfornon-linear
Rule250C&D IncreaseLFforlinear
Non-linear analysis
36
Non-linear analysis
37
Non-linear analysis
38
Furtheranalysisshowedinconsistenciesintheresultsofapplyingthesevalues.
-SomeofGradeCrequirementshigherthanGradeB
-Reducedrequirementsexceedincreased loadduetonon-linear
Non-linear analysis
39
Furtheranalysisshowedinconsistenciesintheresultsofapplyingthesevalues.
-SomeofGradeCrequirementshigherthanGradeB
-Reducedrequirementsexceedincreased loadduetonon-linear
FinalAction:Reject
“Clarification”Determining Gust Response Factor
40
“Clarification”Determining Gust Response Factor
41
Clarifiesusing“spanlength”todetermineGRF
Previouslystatedas“designwindspan”
FinalAction:Accept
Clarify when ice is appliedRule 250D
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…………
Clarify when ice is appliedRule 250D
43
…………
Addiceto:WiresConductorsCablesMessengers
Donotaddiceto:StructureOthersupportedfacilities
Clarify when ice is appliedRule 250D
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…………
Addiceto:WiresConductorsCablesMessengers
Donotaddiceto:StructureOthersupportedfacilities
FinalAction:Accept
New ASCE ReferenceExtreme Wind Map Figures 250-2
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New ASCE ReferenceExtreme Wind Map Figures 250-2
46
2012NESC
2017NESC
ASCE7-05MinimumDesignLoadsforBuildingsandOtherStructures
ASCE74-10GuidelinesforElectricalTransmissionLineStructuralLoading
New ASCE ReferenceExtreme Wind Map Figures 250-2
47
SameMap
NewlyrevisedASCEstandard
2012NESC
2017NESC
ASCE7-05MinimumDesignLoadsforBuildingsandOtherStructures
ASCE74-10GuidelinesforElectricalTransmissionLineStructuralLoading
FinalAction:Accept
New ASCE ReferenceExtreme Ice Map Figures 250-3
48
New ASCE ReferenceExtreme Ice Map Figures 250-3
49
2012NESC
2017NESC
ASCE7-05MinimumDesignLoadsforBuildingsandOtherStructures
ASCE7-10MinimumDesignLoadsforBuildingsandOtherStructures
New ASCE ReferenceExtreme Ice Map Figures 250-3
50
2012NESC
2017NESC
ASCE7-05MinimumDesignLoadsforBuildingsandOtherStructures
ASCE7-10MinimumDesignLoadsforBuildingsandOtherStructures
SameMap
NewEditionofASCE7
FinalAction:Accept
Longitudinal Capability Rule 252.C.6
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Longitudinal Capability Rule 252.C.6
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It is recommended that structures having a longitudinal strength capability be provided at reasonable intervals along the line.
Longitudinal Capability Rule 252.C.6
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LongitudinalcapabilityrecommendationmovedtheissuetoaRECOMMENDATION
FinalAction:Accept
Aeolian Vibration – Rule 261H.1.b
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Aeolian Vibration – Rule 261H.1.b
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Aeolian Vibration – Rule 261H.1.b
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FinalAction:Accept
Aeolian Vibration – Rule 261H.1.b
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FinalAction:Accept
Insulators – New Rating System
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OldLinePostratings:
Ratingequaltoaverage
Lowestnolessthan85%ofaverage
NewLinePostratings:
Rating=Minimumofallinsulators
Insulators – New Rating System
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OldTransmissionSuspensionratings:
1.2standarddeviations
NewTransmissionSuspensionratings:
3.0standarddeviations
Exception AddedInsulator Factory Tests Rule 274
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Exception AddedInsulator Factory Tests Rule 274
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EXCEPTION:
Guyinsulatorsmanufacturedperdesigns
forwhichvalidationtestshavebeenperformed
and
avalidqualityassuranceprogramisfollowed,
thisruledoesnotrequirethat
dryandwetflashovertestsbeperformed
oneachguyinsulatorunit.
Insulators
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CPIntention:
IntroduceLoadfactors(LRFD)
Adjustallowablestresses
Mostlyequivalentinsulatorapplications
IntroduceClasses:Distribution&Trans
Differentallowables forRule250Bvs250C,D
Insulators: Table 253-1 Load Factors
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Insulators: Table 253-1 Load Factors
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Insulators Table 277-1
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Insulators Table 277-1
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Insulators Table 277-1
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Insulators Table 277-1
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Nonceramic Table 277-1 cont’d
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Table 277-1 cont’d
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Table 277-1 cont’d
71
Table 277-1 cont’d
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Table 277-1 cont’d
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FN 3: This percentage shall be supplied by the manufacturer.
FinalAction:Accept
Subcommittee 5 Works in Progress
74
Subcommittee 5 Works in Progress
75
StandardizeTerminology
ImproveClarityandConsistency
K-factor
60ftexclusion
Non-linearAnalysis
GradeN
GradeCx
Subcommittee 5 Works in Progress
76
StartWorkingGroupMeetingsin2016
IEEE WG-7Changes to the 2017 NESC
presented by
Nelson Bingel
Add Temperature Map Figures 250-4For Rule 250D
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Add Temperature Map Figures 250-4For Rule 250D
79
ToBeUsed
With250D
ExtremeIce&
ConcurrentWind
FinalAction:Accept
