04072930

IEEE TRANSACTIONS ON POWER APPARATUS AND SYSTEMS

Standardization of Conductor Vibration

MeasurementsIEEE COMMITTEE REPORT

Abstract-The bending amplitude method is shown to be apractical and simple means for assessing overhead-conductorvibration in all conventional suspension clamps. It has been foundthat the bending amplitude, for all practical purposes, is linearlyrelated to conductor vibration strain, the factor considered mostclosely related to fatigue, and that the relationship is essentiallyindependent of vibration frequency, loop length, conductor tension,and vibration in adjacent spans. The method is recommended,therefore, as a standard for assessing overhead-conductor vibration.A specification for the method is provided along with procedures foranalyzing test data and for inspecting conductors and associatedhardware for the effects of vibration.

IT HAS LONG been recognized that the standardizationlof procedures for assessing the vibration of overheadconductors would provide the industry with much im-proved quantitative information on the various factorsinfluencing the problem and its control. In the past, manymethods, based on the measurement of widely differingparameters, have been used to assess conductor vibration.Therefore, a comparison of vibration survey data underdiffering conditions, e.g., climate, terrain, operating ten-sions, and of the performance of the devices available forvibration control, has been difficult.The present study was initiated by the IEEE Trans-

mission and Distribution Committee for the purpose ofevaluating the various methods available with a view torecommending the standardization of a practical methodof assessing vibration of overhead conductors under fieldconditions. It was hoped that this would be simple to useand would encourage utilities and manufacturers to under-take their own surveys. The methods considered includedthe direct measuremenit of the vibration bending strain inthe conductor close to the point of support, displacement,velocity, and acceleration of the conductor in the first loopfrom the support, and conductor bending amplitude.The latter has been used with success by the OntarioHydro for some 25 years [1]. Although bending strain isconsidered to be the factor most closely related to fatigue,the measurement of this parameter is considered imprac-tical under field conditions except for special investiga-tions. Of the other parameters, the bending amplitudemethod appeared to have the greatest promise since it hasbeen shown to have a predictable and essentially linearrelationship with bending strain and is independent ofvibration frequency and of the articulation of the clamp.

Paper 31 TP 65-156, recommended and approved by the Trans-mission and Distribution Committee of the IEEE Power Groupfor presentation at the IEEE Winter Power Meeting, New York,N. Y., January 31-February 5, 1965. Manuscript submitted October26, 1964; made available for printing February 9, 1965.Members of the Task Force on the Standardization of Conductor

Vibration Measurements of the Towers, Poles, and ConductorsSubcommittee of the IEEE Transmission and Distribution Com-mittee are: E. Fritz, Chairman; A. T. Edwards, A. R. Hard, A. C.Pfitzer, C. B. Rawlins, J. Ruhlman, and J. 0. Smith.

This paper summarizes the results of a study whichshows that the method is suitable for measuring conductorvibration under all service conditions. Procedures foranalyzing the test data provided by the method and forinspecting conductors and associated hardware for theeffects of vibration are also given. The work reported herewas largely performed by Ontario Hydro and much of theother information provided is based on its experience inthe application of the method.

DEFINITION OF TERMS

Bending Amplitude: The total excursion or displacementof the conductor, in mils peak-to-peak, measured relativeto the suspension clamp and at a point 3'/2 inches outfrom the last point of contact between the clamp and theconductor.

Conductor Strain: The maximum dynamic conductorbending strain, in microinches per inch peak-to-peak,measured at or about a suspension clamp.There is also a dynamic-strain component resulting from

tension changes in the vibrating conductor which occursat double the vibration frequency. This strain is small(usually less than 5 percent) compared to the maximumbending strain and, in any case, because of its harmonicrelationship, it does not affect the peak-to-peak value ofthe beniding strain.

STUDIES WITH BENDING AMPLITUDE METHOD

To determine the relationship between bending ampli-tude and conductor strain and its independence of serviceconditions, measurements were made on suitable spans ofACSR conductor, installed as shown in Fig. 1. Each con-ductor was clamped at about mid-span in either a stand-ard articulated suspension clamp or a special unartic-ulated clamp. The clamp elevation in the case of the formierwas adjusted to simulate normal conductor sag for eachtension used. One small-diameter conductor was installedon a pin-type insulator and secured with a pigtail tie.

Resistance foil strain gauges (gauge length, 1/16 inch)were applied to selected wires in the outer layer of eachconductor in the vicinity of the clamping point (shown inFig. 2). Conductor bending amplitude was measured witha linear variable differential transformer attached solidlyto the clamping point. Pickups were also installed on theconductor in the first and second loops on both sides ofthe suspension clamp to monitor conductor velocity. Anelectrodynamic vibration generator was used to vibratethe conductors over a suitable range of frequencies andamplitudes.To obtain consistent results, it was found necessary to

take special precautions to ensure that there was no loose-ness in the individual wires in the test conductors; i.e., the

10

VOL. PAS-85, NO.I JANIJARY, 1966 -

IEEE COMMITTEE REPORT: CONDUCTOR VIBRATION MEASUREMENT STANDARDS

TEST CONDUCTOR DIFFERENTIAL TRANSFORMERAND STRAIN GAUGES LOCATED

'I ENSIONING SCREW ON THIS SIDE OF CLAMP

\VDYNAMOMETERATONARTICULATED SUSPENSION CLAMPGENERATOR

APPROX. 90 FT. -

(I) STRAIN MEASUR8EMENTS AT ARTICULATED SUSPENSION CLAMP

CONSTANT TENSIONVIBRATION TEST UNARTICULATED LEVER ARRANGEMENTGENERATOR CONDUCTOR CLAMP

(2) STRAIN MEAUSREMENTS AT UNARTICULATED CLAMP (ALSO AS IN I)

VIBRATION

PINTYPE INSULATOR/ GENERATOR TEST CONDUCTOR

A RN{ r.,\-DIFFERENTIAL TRANSFORMER

AND STRAIN GAUGES LOCATEDON THIS SIDE OF CLAMP

I-- APPROX. 50 FT. -|

(3)STRAIN MEASUREMENTS AT PINTYPE INSULATOR

Fig. 1. Conductor test span arrangements for dynamic strain measurements.

LOCATION OF STRAIN GAUGESASCR (LOOKING DOWN ON CONDUCTOR

CONDUCTOR IN THE PLANE OF VIBRATION)

P'IGTAILTIE/NO. 4 SOFr DRAWN

ALUM INUM

VO0 SMOOTHBODY SCULPIN 2 3TYPE 150

LAST POINT OF12 INCH BETWEEN GAUGES CONTACT

LOCATED ON TOPOF CONDUCTOR

INS ULATOR

12 INCH BETWEEN GAUGESLOCATED ON TOP OF

CONDUCTOR

533.2 MCM605 MCM

OUTSIDE CLAMP INSIDE CLAMP

LAST POINT OF CONTACTBETWEEN TOP OF CONDUCTORAND SUSPENSION CLAMP

1/2 INCH BETWEEN GAUGESLOCATED ON TOPOF CONDUCTOR

110.8 MCM 0MINORCA X O 4- a1843.2 MCM

OUTSIDE CLAMP INSIDE CLAMP

LAST POINT OF CONTACTBETWEEN TOP OF CONDUCTOR

AND SUSPENTION CLAMP

Fig. 2. Locations of strain gauges on conductors.

TABLE ICONDUCTOR SIZES TESTED

StrandingOutside

Diameter, Number and Diameter,ACSR Conductor Size inches Type inches

1/O smooth body Sculpin 0.388 6 aluminum 0. 1*type 150 11 steel 0.1878583.2 kemil 0.9 418 aluminum 0.18

7 steel 0.06110.8 kemil 0.481 412 aluminum 0.0961

Minorca 7 steel 0.0961

1843.2 kcmil 1.6 472 aluminum 0.16~7steel 0.106754 aluminum 0.1059

605 kemil 0.953 7 steel 0.1059

795 kcml 11 i26 aluminum 0.1749795 keml 1.108 7 steel 0.1360

* Radial thickness.

wires must form a generally tight conductor which usuallyexists under field conditions. Three groups of tests wereperformed:

1) The bending amplitude strain relationship was stud-ied on the driven side (i.e., on the side with the vibrationgenerator) of both articulated and unarticulated clamps.

2) With conductor strain held constant, the bendingamplitude, velocity 2 feet from the clamp, and velocityat the middle of a free loop were measured on both sides ofan articulated clamp. Strain was only measured on thedriven side, at various frequencies.

3) The bending amplitude vs. strain relationship wasstudied on the driven side of an articulated clamp overarmour rods.A list of the conductor sizes tested is given in Table I.

The 1/0 smooth body is the only size tested on a pin-typeinsulator.

111966


b 001.CONDUCTOR ANGLE SET-TO GIVE A

I550- VERTICAL LOADING 0F:700 POUNDS NO.4U ON THE CLAMP

~500

n. GAUGE LOCATIONS ARE SHOWN IN'N.U) 450 FIGURE 2 _

I NO.3z .

a 400 NO.1

C. ;A- -f.,.,350 NO.2t'

z

300 ,*. TS

2 250

>Z .00

H-100 __CONDUCTOR-583.2MCMACSRTENSION -30 PERCENT UTES

u' 50 ARTICULATED SUSPENSION CLAMP

0_0 2 4 6 8 10 12 14 16 18 20 22PEAK-TO-PEAK BENDING AMPLITUDE RELATIVE TO CLAMP IN MILS

Fig. 3. Typical strain-bending-amplitude relationship on a conductor.

DISCUSSION

Test results, (shown in Fig. 3), show that the strain-bending-amplitude relationship is essentially linear, partic-ularly up to amplitudes of about 10 mils. At greater ampli-tudes, the strain generally drops off -slightly, although notsignificantly. Since most conductors either are operatedat low tensions at which vibration levels are normally ata low level, or are provided with dampers or reinforcingdevices, the amplitude range of interest is usually between5 and 20 mils. The relationship is essentially independentof the following factors:

Vibration Frequency: Figures 4 and 5 show the negligibleeffects of frequency over a wide frequency ranige on twoconductor sizes.

Tension: Figure 6 shows the estimated relationship be-tween bending anplitude and the conductor wire diameterfor a constant bending strain of 150 min/in peak-to-peak(see following discussion). Also plotted on this figure are

the measured bending amplitudes for a number of conduc-tors at different tensions. These indicate that bending strainis independent of tension over the range of 15 to 30 percentultimate tensile strength (uts).Span Length: On a given conductor at constant tension,

both the sag angle at the suspension clamp and the ver-

tical load on the clamp increase with span length. Thestrain-bending amplitude relationship was found to beessentially independent of these parameters for normalspan lengths and tensions.

Vibration Levels in Adjacent Spans: Figure 7 shows that,while a conductor is vibrated at various frequencies andthe conductor strain is held constant at the suspensionclamp, the bending amplitude also remains essentially con-

stant despite the large variation in the relative vibration

Y-ICw

(LI

w

W-

7

Z)it

'4OTE-

;400 1.

2. TESTS WITH BOTH PIGTAIL TIES AND LONG TOPTIES GAVE THE SAME ORDER OF DYNAMIC STRAIN

3. THE STRAINS VARIED FROM THE AVERAGE BYABOUT ± 14 PER CENT ON SAMPLE LOTS OF FIVE

.300 TIES OF EACH TYPE

It-

U)

0:

z

0

0 0

20 40 60 80 100

VIBRATION FREQUENCY IN CYCLES PER SECOND

Fig. 4. Maximum dynamic strain vs. vibration frequency on 1/0smooth body ACSR conductor at 30 percent uts.

IL

4(

NC

U)

(LJLU

z

U)

0 10 20 30 40 50 60VIBRATION FREQUENCY IN CYCLES PER SECOND

Fig. 5. Maximum dynamic strain vs. vibration frequency on 605-kemil ACSR conductor at 30 percent uts.

levels of the conductor on both sides of the clamp. Thisfigure also indicates that conductor displacement, velocity,and acceleration in the first and second loops are notlinearly related to bending strain and, therefore, are not

particularly suitable parameters for assessing conductorvibration.Clamp Effects (All Metal Clamps): These include normal

clamp pressures, articulation rigidity, and mouth radii.Tests carried out on unarticulated clamps with variousmouth radii showed that the strain-bending-amplituderelationship was constant with radii ranging from 1/64inch to 6 inches. Nevertheless, it is considered good prac-

tice to provide generous radii at the mouths of all con-

ductor clamps in order to prevent conductor damageby sharp edges.

Effect of Armour Rods: Figure 6 shows that, on a 795-kemil conductor, the relationship was not affected by the

00

20

NOTE:

BENDING AMPLITUDE HELD CONSTANT AT 8 MILS

00 o0

0

0 --1 - -1

12 JANUARY

121

5c

.^An


0.00CONDUCTOR OUTER LAY WIRE DIAMETER IN INCHES

Fig. 6. Correlation of calculated and measured "safe" bending amplitudes.

0 10 20 30 40 50 60VIBRATION FREQUENCY IN CPS

Fig. 7. Correlation of constant bending strain with bending ampli--tude and velocity on 1843.2-kemil ACSR conductor with con-ventional clamp, 30 percent uts.

application of armour rods. It is interesting to note thatthe maximum strain measured on the armour rods alsofalls on the curve.

The results also show that the strain-bending-amplituderelationship is a function of the wire diameter in the outerlayof the conductor (Fig. 6), i.e., for a given bending ampli-tude, the strain is proportional to wire diameter. Correlationof the measured and calculated relationships between bend-ing amplitude and outer-layer wire diameter for a maxi-mum bending strain of 150 ,uin/in peak-to-peak is shownin Fig. 6. The calculated values (see Appendix) are basedon the observations

1) The bending slope of the conductor, with respect tothe clamp, approaches that of a cantilever beam with auniformly distributed load.

2) The individual wires act essentially independently.Hence, the distance from the neutral plane to the mostdistant fiber is equal to half the wire diameter rather thanhalf the conductor diameter. The strain calculation in-cludes an experimentally determined factor of 1.4 to allowfor the clamp effect which appears to restrict, somewhat,the independent motion of the wires at amplitudes belowabout 15 mils.Thus, the contention that the vibration bending strain

1966 13

z

(I)

IX<:<L

LU0oF-L ycY <

<Ik0

Ye X<L

DU)

z- uZ

0w In

zLUa

20X 15 PERCENT UTS

CONDUCTOR STRAIN 0 20 PERCENT UTS030 PERCENT UTS

o 20 AND 30 PERCENT UTS WITH ARMOUR RODS

16 A ARMOUR ROD STRAIN

THE CURVE WAS CALCULATED ASSUMING 140PERCENT OF THE THEORETICAL STRAIN WITHNO INTERWIRE FRICTION (SEE APPENDIX)

12

V0 SMOOTH BODY

8 r e r 605 MCM |

10. 8MCM MINORCA 5 MCM

4

.__ __1842_3 MCM II

60

LaiaI.y

150

waI.az0Q 40U)

LiILIU)LU'r30

THICK LINE-DRIVEN SPANTHIN LINE-DEAD SPAN

SBENDING AMPLITUDE----VELOCITY 2 FT FROM CLAMP MOUTH

.,.VELOCiTY MID LOOP IN FREE LOOPZ

NOTE - THE STRAIN-BENDING AMPLITUDE RELATIONSHIP ISESSENTIALLY CONSTANT AND IS INDEPENDENTOF THE RELATIVE CONDUCTOR VELOCITIES ON EITHERSIDE OF THE SUSPENSION CLAMP

leLIC

ELU

I-

J

zhi

tLU I

-J

Cl

z

0

zax

g

HV-z0a)

i0.05 0.10 0. 15 0.20 0.25 0.30 0.35


for a given bending amplitude is proportional to wirediameter and independent of conductor diameter is well,supported by the excellent correlation obtained betweencalculated and measured strains on conductors having awide range of both wire and overall diameters.The maximum bending strain that can be tolerated in

ACSR conductor without eventually inducing fatiguedamage cannot yet be stated precisely. The tolerablestrain is, in fact, part of the information which it is hopedwill be obtained by the general use of the standardizedmethod of measurement. There is also the possibility thatthe accumulative rate of vibration cycles may be takeninto account in determining the maximum safe strain fora given location. This is one of the reasons for measuringthe frequency of the vibration.For the purpose of this analysis, however, a strain of

150 min/in peak-to-peak has been selected on the basis thatthe bending amplitude required to produce this strain (5'/2mils) in 795-kemil 54/7 ACSR (wire diameter 0.1214 inch)has not produced fatigue damage in conductors, in con-ventional suspension clamps in the field after 30 years ofservice [2]. Recent measurements on the cable absorber,also referred to in [2], have shown a maximum bendingamplitude of 14 mils for which the corresponding esti-mated dynamic strain range is about 300 Ain/in peak-to-peak. This produced a moderate number of fatigue failuresafter 30 years service. It is speculated, therefore, that thevalue of 150 min/in, which is given here only as a guide, issomewhat conservative and that strains of the order of 200,uin/in peak-to-peak may well prove to be safe. Until moreprecise information is made available by the general use ofthe method, local experience and other factors, e.g.,security requirements, will necessarily dictate the level ofstrain considered safe and how frequently this may besafely exceeded.The strain-bending-amplitude relationship presented

here is only applicable, of course, to conductors supportedin conventional clamps with or without reinforcing rods,and to conductors in ties. The relationship would requiremodification for application to other supporting systemssuch as those incorporating rubber members.These studies show clearly that the bending amplitude

is a suitable parameter for assessing conductor vibration.The method, as described, will also provide information onthe frequency spectrum of the vibration. This will greatlyassist the assessment of local conditions, e.g., terrain, andthe specification of vibration protection requirements orthe modifications to an existing system if this is consideredto be inadequate. An illustration of this last considerationis given in Fig. 12 which indicates that the low-frequencyperformance of the dampers needs to be improved.

STANDARD BENDING AMPLITUDE MEASUREMENTSThe sampling procedure for assessing conductor vibra-

tion is designed for obtaining, in the minimum time, thenecessary information on bending amplitude and fre-quency. Three parameters are involved, namely the timeinterval required for individual records in the sample, the

number of records per hour, and the total length of thetest period in days.

Time Interval

Examination of a typical vibration record severalseconds long, such as the sample shown in Fig. 8, showsthat it has a characteristic modulation with peak ampli-tudes recurring at time intervals which are usually lessthan 1 second. A record at least 1 second long should,therefore, provide a representative sample of the short-term vibration.

Number of Records per HourFor many years, bending amplitude sampling carried

out by Ontario Hydro was based on only two records perhour. The standard rate was changed to four records perhour, however, after a study showed that this frequencygave slightly more accurate results. Typical results from aseries of sampling-rate tests on a 795-kemil ACSR con-ductor are shown in Fig. 9. A sampling rate of four recordsper hour was used, but the records were also analyzedusing odd and even numbered records to produce two morecurves, each based on two records per hour. These resultsshow the slight increase in accuracy obtained by using fourrather than two records per hour.

Test Period

Since conductor bending amplitude at a given dampinglevel is a function of wind speed, direction, and turbulence,its maximum value is not reached on every test day. Ex-perience has shown, however, that under normal conditionswith winds predominantly steady and less than, say, 10mi/h, the maximum bending amplitude is usually recordedif the test period is one to two weeks long. Measurementson an undamped 1400-foot span of 795-kemil ACSR con-ductor tensioned to 25 percent uts at 60°F showed thatthe maximum bending amplitude reached in a continuousperiod of 68 days was 26 mils. An analysis of the dailyrecords showed that the percentage chance of recordiig abending amplitude of at least 90 percent of 26 mils risesquickly as the test period increases (see Fig. 10) and ap-proaches 100 percent for a test period of 14 days. A testperiod of at least two weeks is therefore suggested forassessing conductor vibration.

FIELD MEASUREMENTSThe suggested test procedure for most field investiga-

tions is as follows:

1) Select the span or spans to be tested. Where the pur-pose is to determine if vibration protection is satisfactory,the spans with the greatest exposure should be tested, i.e.,spans located on relatively flat ground and well above oraway from trees or other obstructions. If selective damp-ing is planned on the basis of exposure, both exposed andshielded spans should be checked.

2) Check the mechanical tension of the conductor tomake sure that it agrees with the stringing specifications.

14 JANUARY


I 0.6 SECOND

5ECOND

Fig. 8. Characteristic pattern of bending amplitude in relation tostandard l-second record length.

z

O 0.1

S0 O. 8 ____ ___} 2 RECORDS PER HOUR

C] 4RECORDS PER HOUR

xL 0.6 - TESTS CARRIED OUT ON A 1400 FT. SPANOF 795 MCM,ACSR CONDUCTOR AT A

0 ~~~~~TENSION OF 25 PERCENT UTS.z0

L 0.4

E L05010___20225

BENDING AMPLITUDE IN MILS PEAK-TOPEAK

Fig. 9. Sampling test to determine optimum nulmber of records perhour.

This may be done by either the sag or pulse method andcalculated by:Sag M\ethod:

Conductor tentsion, pounds =(conductor lb/ft) X (spani, ft)2

8 X (sag, ft)

Pulse MViethod:

Conductor tension, pounds =

(conductor lb/ft) X (span,8.05 X (period, s)2

The pulse method is usually more convenient for use inconjunction with vibration measurements but, becauseof the resulting reflections, cannot be applied if there are

one or more joints in the span.

The period is the time in seconds required for a pulseto travel from one end of a span to the other end and toreturn to its starting point. The recommended methodfor measuring the period is to strike the conductor sharplyat a point, 1 or 2 feet out from the suspension clamp,with a piece of wood or a hot-line stick and simultaneouslyto start a stopwatch. The watch should be stopped tocoincide with the return of the pulse after it has madeseveral trips along the span. The more return trips thatcan be included before the pulse dies out the more accuratethe measurement is likely to be. For example, if the pulsemakes five return trips in 20 seconds, the period is 4seconds and the tension can be calculated by using thepreceding equation. The pulse test is best carried out on a

conductor without dampers but it can be difficult duringperiods of severe aeolian vibration. One damper attachednear a suspension point will usually reduce the vibration

I-z

as.c-

(9 Z

DZEW

a: D

6 x

Lu

zI

0<r:

80 2 4 6 8 10 2 14TEST PERIOD IN DAYS

Fig. 10. Percentage chance of recording maximum bending amplitude.

sufficiently to allow the pulses to be counted. If the spanis heavily damped, however, the pulses will be absorbedand it may be difficult to obtain a measurement for evenone period.The temperature should be recorded at the time of teti-

sion measurements. If the vibration measurements aremade during a period of relatively high temperature, andthe tension is therefore not at the maximum bare-conduc-tor value reached at the lowest winter temperature, thebending amplitudes on undamped conductors, includingthose protected with armour rods, may be adjusted fortension by assuming that the maximum bending ampli-tude is proportional to tension squared. This adjustmentappears to be approximately correct for conductors up toabout 336.4 kemil. Above this size, there is an overestima-tion of the amplitude for increased tension. For example, ifa maximum bending amplitude of 15 mils is measured onan undamped conductor tensioned at 18 percent uts, thepredicted bending amplitude at a tension of 20 percentuts would be (15 + 202)/182 = 18.5 mils. In critical situa-tions, it is preferable, of course, to make the vibrationmeasurements at or near the period of lowest temperatures.

3) If the conductors are undamped or are protectedonly by armour rods, the recorders may be installed andthe test started. Experience has shown that it is usuallybetter to instrument two or more conductors at one tower,not only to reduce installation time but also to confirmthat each of the conductors vibrates at typical amplitudesand that no other complicating factors are present.

4) Where the conductors are provided with separatedampers, it is suggested that, for the first test period, thesedampers be removed from the test span and from atleast one adjacent span on each side of the test span toestablish that each conductor in the undamped condi-tion vibrates "normally" [2].

151966

16

CONDUCTC SIZE -1.6 ACSR


TABLE ItCONDUCTOR VIBRTION TESTS

TEST_SPAN - LINE L19K LAKEVIEW - MANBY TOWER NO 19

FUUIOUENC BENDING AMPLITUDE IN INCHES PEAK TO PEAK Mc Mc

0.0W 0.002 0.003 .00410.005 0.006 0.007 0.006 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016 0.017 RE) ACP_ _ EO._PER___^ &._DAY~~~~~~~~~~~~~~~~l OR4WO.- Ve _ v eV.Wes i_ ~VVWwEW

2 1 + .0036 _009 .0036 .0162 .0011

4 l _ .010 60 0334 DIM 018 2 DIM .1414 .0094

_ _ 01ffi Q43 .1Q16 !080 lL0 .34D .0182 .0918 .0270 D162 .0162 054 .646 .043Is _ 360 .0936 0936 .0936 1368 J440 .1440 .1008 .0864 .0648 .0432 P44 P0072 L0584 .0705

10 2 .1476-oo-= .jw .1530 J98o .*If .28o 3600 3150 .2520 .1800 .0810 450 8 60 .0270 2.2140 .1476

12 2 0216 .1728 1296 iJ620 .1080 r7 56 .0648 .1080 .0216 .0216 P1O8 .8964 .0597

14 2 19399 .06671.012J ., 45 ,s.71 .030 0126 .0126 .9.. .0

Js 3 > .1152 172 .1584 440 P720 1.0720 0432 .0144 .8064 .0538

1 081 0 486 .0324 TP32 40324 r .1944 .0129

20 .1260 J260 __2520__016822 LI386 P782 .3168' .0211

.1512 .1512 .0101

26 .0702.____ _ _ .0702 .0047

28 02 .0252 .0017

30 .1080 .0072

32

< < 9 ,:

36 7

381 7

40

42 8

44 8

46 9

48

Mc(AMP) 94 8883 L0233 1.0071 0252 .7074 7416 .6300 5034 3042 .1620 .0936 .0540 R570 .0270 .0090Mc

(~ft D^y) 580 0592 OS82 J O55 |472 0494 .0420 0334 .0203 .0I08 .0062 .0036 .038 ,OOI8 .0006 __

ACCUM 5266 A686 94 2 .2741; 2191 .1719 1225 0S P471 .0268 .0160 0098 |.0062 .004 .0006

ANALYSIS OF TEST RESULTSThe following is a suggested method for detailed anal-

ysis of vibration records. Results from a test of experi-mental dampers on an 1843.2-kemil ACSR conductor are

used to illustrate the procedure.Step 1

Measure the maximum peak-to-peak amplitude andthe frequency for each record. Insert the results in TableII (undamped) and Table III (damped), as shown. For thepurpose of this analysis, the conductor is assumed tovibrate for 15 minutes at the maximum bending amplitude

measured in each 1-second record. One dot in each boxrepresents one record at that amplitude and frequency.To save space in these tables, double scales are providedfor both frequency and amplitude. On the fine scales, bend-ing amplitudes up to 17 mils may be recorded to the near-

est mil and frequencies up to 48 c/s may be recorded tothe nearest even frequency. The coarse scales are providedfor higher amplitudes and frequencies. Scales not usedshould be crossed out.

It is often possible to stop the analysis after completionof step 1 since the pattern formed by the dots provides a

good indication of the maximum amplitude and frequency

TEST N6IB1DATE-SIEPT.20-CT.I143 1 N. DAYS-IS I SPAN-1036 FT. I TENSION-22% UTS I AMPERS -UNDAMPED

JANUARY

.0I


TABLECONDUCTOR VIBRATION TESTS

CONDUCTOR SIZE - 1.6 TEST SPAN- LINE L19K LAKEVIEW - MANBY TOWER NO. 19

distribution of the vibration. For formal presentation ofresults, however, it is recommended that the analysis becarried through to step 10. In this example, Tables II andIII show that the dampers are effective at the higher fre-quencies but that they are less effective at frequencies up

to 6 c/s.

Step 2

Using the assumption given in step 1, convert the dotsin each box into megacycles and insert the figure in the boxunder the dots, e.g., 1 dot at 10 c/s = 0.009 Mc; 2 dotsat 10 c/s = 0.018 Mc. A table can be prepared to facilitatethis computation.

Add all the figures in the boxes horizontally oppositeeach frequency and insert the totals in the vertical columnheaded Mc (Freq).

Step 4Divide the totals by the number of days in the test

(14 in this example) and insert the results in the nextvertical column headed Mc per day.

Step 5

Add all the figures in the boxes vertically under eachamplitude and insert the totals in the line Mc (Amp).

TEST NO. I DATE - WOV.22-DEC.5/63 NO. DAYS -13 | SPAN -1036 FT| rENSION- 22% UTS I DAMPERS - 2/%PAN@8'

FREQUENCY BENDING AMPLITUDE IN INCHES PEAK TO PEAK MC MC0.001 Qw0.003 0.0 40.005 0.0060.007 .o0v8 0.009 0.010 0.011 0.012 0.013 0.014 0.015 0.016 0.017 (FREQ)PER DAYV* OS V.Voe V0 VVV.VV,V4I iV OtS. . 3O 5V81 Vt BO21 V.* 3* V.w .Oe4 WI V. W 8s V.63 W ___

2 -_-_- __ __ - e - _e _e - -

4§ w | @1-@' v 1@-- ' @ v

.3024 .0233____ __ .07 92 .0900 .0396 .0250180 .0288 .0036 .0072 .0072 .0036 .3 .02336 I .3348 .0258.0540 .1188 .1026 0270 .0216 .00541.0__0______8 I6 .0144 .0144 .0011

10 2) 05 03070- -0090 .0090.05 .03

22 44

12C .01962 .032096 _.1692 .OS22_ .054 96.3.0009420 00 .0

24 2

26 5 02.0468.00)3

28 36

20 60.0180 1-°4 .18 .aO Dll

32 22

24 6

26 706 06 03

28 7

30

32 8

344

46

48

Mp .1962 .3096 J692 .0522 .0396 .0342 .0090 .0072 .0072 .00361McPRDY 0151 .0238 .0130 .0040 .0030 .0026 .0007 .0006 .0006 .0003

ACCUM .0637 .0486 .0248 1.0118 .0078 1.0048 1.00221.0015 .0009 .00031

1 966 17


Step 6

} ,

0IU)Wi 0.7Q

I-<0.3

ES ~~UNDAMPED

Z 0.3 ".aw

U 0.2 STWO DAMPERSPER SPAN

0 I0 2 4 6 8 10 12 14 16

BENDING AMPLITUDE IN MILS PEAK-TO-PEAK

Fig. 11. Accumulative vibration.

18

Fig. 12. Maximum bending amplitude vs. frequency.

15 20 25 30FREQuIENCY IN CPS

Divide the totals by the number of days and insert theresults in the next horizontal column headed Mc per day.

Step 7

Insert the accumulative figures in the next line headedaccum. The method followed is to start at the right-handside (highest amplitude) and work towards the lowestamplitude. The accumulative figure is always the total ofthe box above plus all figures to the right of this slot(see example).

Step 8

On Fig. 11, plot the accumulative figures (derived instep 7) against bending amplitude.

Step 9

On Fig. 12, plot the maximum bending amplitudethat occurred at each frequency.

Step 10

On Fig. 13, plot the megacycles per day (derived in step4) against frequency.

Figures 11, 12, and 13 contain all the information re-quired for a formal presentation of conductor vibrationconditions.

VIBRATION RECORDER SPECIFICATIONSThe following is a specification for an instrument in-

corporating the bending amplitude method: It should becapable of being installed on a live conductor at a supportpoint without taking the line out of service; once in posi-tion it should automatically sample conductor bendingamplitude for a minimum of 1 second every 15 minutesfor a period of at least 2 weeks; on completion of the test,it should be capable of being conveniently removed fromthe live conductor for purposes of removing the vibrationrecord and replenishing batteries, etc. Detailed specifica-tions are given in the following.

LIVE-LINE VIBRATION RECORDER SPECIFICATIONSFeatures and Requirements

1) Recording system: Should provide a record of vibra-tion bending amplitude' and frequency. (For convenienceit is preferable to be able to examine records in the fieldwithout the necessity for chemical processing.)

2) Record length: 1-second minimum.3) Records per hour: 4 minimum.4) Recording period: 14 days minimum.5) Maximum bending amplitude: 50 mils minimum. (An

allowance of at least +15 mils should be made to accom-I Bending amplitude is the total excursion or displacement of the

conductor, in mils peak-to-peak, measured relative to the suspensionclamp and at a point 3'/2 inches out from the last point of contactbetween the clamp and the conductor.

a

wIL

Fig. 13. Megacycles per day vs. frequency.

18 JANUARY


modate sag changes with temperature. The record widthshould therefore accommodate 80 mils minimum.)

6) Bending amplitude readout sensitivity: to the near-est 0.5 mil.

7) Frequency response: +t10 percent from 0 to at least150 c/s.

8) Frequency readout: 1 to at least 150 c/s.9) Mechanical impedance of recorder driving arm and

conductor clamp (if any) attached to the conductor at thestandard 3'/2-inch point:2 Must not affect bending ampli-tudes on the smallest undamped conductors by more than10 percent.3

10) Temperature range: Suitable for local ambient tem-perature range. (-40 to 150'F is a suitable range forgeneral use.)

11) Weatherproofing: Must prevent rain leaks undernormal conditions.

12) Conductor range: Minimum, conductors of 0.09 lb/ft; maximum, no limit.

13) Weight of recorder plus installation fittings: Pref-erably 20-pounds maximum.

STANDARD FIELD INSPECTION FORMLines surveyed for conductor vibration should, at the

same time, be inspected to determine the condition of theconductors and hardware. Experience has shown thatreliable records of field inspections are very difficult to ob-tain and that pertinent information is seldom complete.The field inspection form (shown in Figure 14) was pre-pared to provide guidance to inspection crews on the pre-cise information required and to facilitate recording ofthis information. It is recommended that this form berecognized as the industry standard.

CONCLUSIONThis study has shown the bending amplitude method to

be suitable for assessing overhead conductor vibration;the method is recommended for adoption as a standard.Although it is directly applicable at present only to con-ventional clamps (with or without armour rods), studiesare in progress which are likely to result in its applicationto other supporting systems, such as those incorporatingrubber members. As the method becomes generally ac-cepted, the industry is expected to benefit greatly by the

2 If attached at a point other than 31/2 inches from the last pointof contact the recorded amplitude should be convertible to thestandard measurement.

3Experience shows that this condition will be met if the mass,stiffness and particularly the damping of the moving parts are keptto a reasonable minimum. It may be checked by comparing recordermeasurements against those made with a suitable linear variabledifferential transformer on successive test periods. A recorder witha driving arm spring rate of 260 lb/in and an effective drivingassembly weight of 0.5 lb has been found suitable for use on con-ductors down to No. 2 ACSR provided the damping (energy dissi-pation) in the moving parts in free vibration, i.e., with the recorderisolated from the conductor, is such that a minimum of four cyclesare required for a 50 percent reduction in amplitude. The recordercan be electrical, mechanical and/or electronic. An example of anelectromechanical recorder meeting the above specifications isdescribed in [3].

information that it provides. Eventually, it will be possi-ble to design vibration control for overhead conductorswith a greater degree of confidence than generally existsat the present time. It is further recommended that pro-cedures be made available through the IEEE for the col-lection and analysis of conductor vibration data togetherwith inspection information so that summaries may bemade generally available to the industry.

APPENDIXThe maximum strain in a vibrating conductor at the

mouth of a suspension clamp is essentially a function of thebending amplitude and the distance from the neutral bend-ing plane to the most distant fiber, which acts in conformitywith the usual beam theory assumptions. If it is assumedthat no interwire friction exists, this distance is half thewire diameter because the individual wires act independ-ently. If it is assumed that no interwire slipping occurs,then the distance to the outermost fiber is equal to halfthe conductor diameter because the conductor behaveslike a solid bar.

These assumptions lead to two estimates of strain whichbracket the range in which the actual strain should occur.Take the general case of a D-inch-diameter conductor hav-ing outer-layer wires of d-inch diameter. Examination of avibrating conductor about a clamp shows that the curva-ture approaches that of a cantilever 3'/2 inches long witha uniformly distributed load. If this distributed load isW lb/in, then, from standard beam theory:

1) The maximum bending moment M = WL2/2,where L = 31/2inches.

2) The displacement from neutral axis at 31/2 inchesfrom last point of support Y = WL4/8EI, where E is theYoung's modulus, lb/in2, and I is the moment of inertia ofsection, in4.

3) The maximum conductor stress is MC/I where C isthe distance in inches from the neutral axis to the outer-most fiber.

4) Therefore, the maximum conductor strain is equal toMC/EI.

5) Substituting for M and EI from (1) and (2): maxi-mum conductor strain is 4CY/L2 peak or 0.654CY peak-to-peak. Since bending amplitude is 2Y, peak-to-peakstrain in microinches per inch is 327C (bending amplitudein mils peak-to-peak).

Correlation of strain measurements with calculationsbased on these equations shows that the measured valuesare slightly higher than those obtained with C = 0.5d,where d is the wire diameter in inches. Apparently, theconductor clamp somewhat restricts the individual motionof the wires at amplitudes below approximately 15 mils.In order to allow for this effect, an experimentally deter-mined multiplyingfactor of 1.4 is used. Thestrain-bending-amplitude relationship is then given by: peak to peakstrain in microinches per inch = 230 X individual wirediameter in inches X bending amplitude in mils peak-to-

1966 19


OONDUCTOR FATIGUE INSPECTION SHEETFOR TRANSMISSION CONDUCTORS

AND GROUND CABLES(ONE SHEET FOR EACH CIRCUIT ON EACH TOWER)

DATESHEET

INSPECTORtS NAME

LINE SECTION AVERAGE SPAN FTCIRCUIT CONDUCTOR COPPEROPERATING VOLTAGE KV ALUMFROM ACSRTO CONDUCTOR SIZE MCMTOWER NO. CONDUCTOR STRANDING ALUMSTEEL ST.ELWOOD GROUND CABLE SIZE MCM oIN-SERVICE DATE IN. 00

CABLE STRANDING ALUMSTEEL

SECTION 2 -SAGSAND TENSIONS

SPAN-FT SAG - FT PULSE TIME DEGREES F SAG SHEETI ~~~~SECS *NO.

CONDUCTORGROUND CABLE

SECTION 3 -TERRAIN- ONE SIDE

FLAT ROLLING OPEN_ TREES - BOTH SIDESSECTIO14N 4-SUPPORT HARDWARE

SUSPENSION CLAMP CLAMP TIGHTENING TORQUE ONMFR. AND DESIGNATION BEARING GALV CLAMP BOTSOR TYPE NO. LENGTH-INCHES ALUM IRON (IN. LB.)

CONDUCTORGROUND CABLESECTION 5 - VIBRATION PROTECTION

REINFORCING DAMPERS*

NONE FESTOO PREFORME A PERED OTHER ORSIONAL STOCK-ROD RODS BRIDGE CAL OTECONDUCTORGROUND CABLESECTION 6-DAMAGE UNDER TOP OR CENTRE OR BOTTOM OR GROUN CABLESUSPENSION CLAMP** LEFTW* PHASE MIDDLE PHASE RIGHT PHASE

_LEF RIGHTNO. OF BROKEN WIRESNO. OF PARTLY CRACKED WIRESNO. OF WORN OR ABRADED ORNICKED OR RUBBED WIRESNO APPARENT DAMAGESECTION 7 - DAMAGE IN SPAN**(UNDER REINFORCING ETC.) TOPOR CENTREOR BOTTOM OR GROUND CA1BLE

LEFT PHASE MIDDLE PHASE RIGHT PHASE LEFT RIGHTCONDUCTOR DAMAGEDREINFORCING ETC. DAMAGEDNO APPARENT DAMAGE TOCONDUCTOR AND REINFORCINGSECTION 8 - REMARKS

ONTARIO HYDRO RESEARCH DIVISIONJUNE 1964

* INSERT NUMBER PER SPAN** NOTE LOCATION EG I WIRE AT 12 U/C (OCLOCK) 2 WIRES AT 4 U/CLOOKING TOWARDS THE POWER SOURCE

Fig. 14. Field inspection form.

peak. This indicates that, for a given bending amplitude,the strain is directly proportional to wire diameter andis independent of conductor diameter.

REFERENCES[1] G. B. Tebo, "Measurement and control of conductor vibration,"

Trans. AIEE, vol. 60, pp. 1188-1193, December 1941.[2] J. E. Sproule and A. T. Edwards, "Progress towards optimum

damping of transmission conductors," Trans. AIEE (PowerApparatus and Systems), vol. 78, pp. 844-852, October 1959.

[3] A. T. Edwards and J. M. Boyd, "Ontario Hydro live-line vibra-tion recorder for transmission conductors," IEEE Trans. onPower Apparatus and Systems, vol. 82, pp. 269-274, June1963

DiscussionB. Hondalus (Reynolds Metals Company, Richmond, Va.): TheTask Force Committee has recommended acceptance of the bendingamplitude technique as the industry standard method of measuringconductor vibration. This is the most significant forward step evertaken by our industry toward solving the problem of conductorvibration.

Standardization furnishes a means for correlating, on a commonbasis, field and laboratory conductor vibration data collected bymany organizations and individuals from different transmission

Manuscript received March 5, 1965.

20 JANTUARY


lines throughout the country. With such a massive and effectivetool available to the industry, the problem of conductor vibratioris closer to being completely resolved.

For about two years, in my own company, we have been usingthe bending amplitude technique, both in the laboratory and in thefield, and we are convinced that it is technically sound.We have used self-contained recording instruments of the type

specified by the committee and have found them to be reliable andrelatively trouble-free. At first, we were concerned that the specifiedvibration sampling of a single 1-second record, each 15 minutes,was inadequate for accurate evaluation. However, experience hasproved that excellent repeatability is obtained using this procedure.The 2-week recording period has also been found satisfactory. Infact, a 1-week recording period gives almost as good results and ithas been used in emergency situations. We have monitored a numberof vibrating transmission lines in different areas of the country usingthe bending amplitude method and, on this basis, have made recom-mendations for corrective action. The method is simple to useand relatively inexpensive; in addition, it allows engineering recom-mendations to be made on a solid basis.

Particular emphasis should be placed on the authors' statementthat "The maximum bending strain that can be tolerated in ACSRconductors without eventually inducing fatigue damage cannot bestated precisely." For aluminum conductors, the tolerable bendingstrain limit is generally believed to be in the range of 150 to 200,uin/in. However, this limit is still an estimate and further workis needed to define more precisely the fatigue limit of different con-ductors. When this is accomplished, vibrating conductors willcease to be a problem because sufficient information will be availableto control them adequately.

G. H. Weldon (Manitoba Hydro, Winnipeg, Manitoba, Canada):The method described in this paper for measuring conductorvibrations in the field on live transmission lines has beenused by Manitoba Hydro for the past year and a half. The vibrationrecorders being used for these conductor vibration measurementswere designed by Ontario Hydro, and the results to date have beenmost gratifying. This recorder is relatively simple to install, is rugged,and requires very little maintenance.The adoption of this recorder for general use by utilities would

be a big step forward in solving the conductor vibration problem.Pooling of the information obtained would aid line designers through-out the continent. In this way, not only could existing vibrationproblems be correctly analyzed but experimental work in the designof new damping techniques would be assisted.

In our case, we have not been able to find any relation betweensummer and winter readings with the recorder. The authors havestated that, if the vibration measurements are made during a periodof relatively high temperature, and the tension is therefore notat the maximum value reached at the lowest winter temperature,the bending amplitudes on undamped conductors may be adjustedfor tension by assuming that the maximum bending amplitude isproportional to tension squared. The maximum amplitude measuredwith the recorder was 51 mils at a tension of 20.6 percent of ultimatetensile strength and a temperature of 63°F for a 336.4-kemil ACSRundamped conductor. At 24.5 percent of ultimate tensile strength,which is the conductor tension corresponding to a temperatureof - 15F, the maximum amplitude would then become 51 X 24.52/20.62 = 72 mils. A winter recorder reading at - 15F indicated amaximum amplitude of 80 mils, which approximates the calculated72 mils. However, recorder readings taken during the summer with2 dampers per span indicated a maximum amplitude of 12 mils at atension of 20.6 percent and a temperature of 63°F. At a tension of 24.5percent of ultimate tensile strength, temperature - 15F, the maxi-mum amplitude recorded was 30 mils. There does not appear to be

any significant relationship between the summer and winter recorderreadings of vibration amplitude of the damped conductor. Is thereany way of calculating the damped vibration amplitudes if theundamped amplitudes are known? Our very severe vibration condi-tions (long periods of extremely low temperatures accompanied bysteady winds of 10 to 15 mi/h) indicate that most of our recordingsmust be taken during winter months to obtain a proper analysis ofthe vibration level.

E. Fritz (Orange and Rockland Utilities, Inc., Middletown, N. Y.):During the summer of 1960, I was asked to head a group of AIEEmembers who were to study the feasibility of standardization ofconductor vibration measuring devices, with an eye to seeing if theindustry could do a better job of predicting conductor fatigue.Our first step was to distribute a questionnaire to 23 experts,

who had prepared papers on aeolian vibration or were associatedwith manufactfiring companies interested in this field. The question-naire listed seven stress relationships reported to be associated withconductor fatigue and requested an expression of the relative impor-tance in predicting fatigue of each of these and the best procedurefor measurement.

Replies were received from 16 experts. The divergence of opinionregarding the factors that were most important to measure as wellas the lack of acceptance of measurement devices lead me in myfirst report to the Towers, Poles, and Conductors Subcommitteeto suggest that the task force be instructed to standardize datarecording procedures, rather than attempt to standardize measuringdevices not generally accepted by the industry. It is of interest.that, in addition to the seven fatigue culprits of the questionnaire,several experts indicated that conductor element fretting is alwayspresent in conductor fatigue breaks and that fretting would alsohave to be "subpoenaed" before fatigue breaks could be "arrested."At the 1961 meeting of the Task Force, the group decided to

attempt to establish whether or not a linear correlation exists be-tween differential displacements which could be measured byamplitude and frequency counting devices and dynamic strain asmeasured by the strain gauge. One member was commissioned tosubmit a standardized list of field measurement items which shouldbe recorded before analysis of vibration activity on existing linescould be expected to lead to meaningful predictions of conductorfatigue.The paper is the committee report covering the success of both

of these efforts. This report was read by Mr. A. Edwards of theHydro Electric Power Commission of Ontario who, with Mr. J. M.Boyd, Ontario Hydro, prepared the major portion of this report.Mr. Edwards, in his presentation, stressed additional data and

findings which Ontario Hydro have developed in their laboratorypertinent to our project; these data were deleted from our reportin order to reduce the size of the paper. Some of these findings hadnot been confirmed by other members of the committee at the timeof our last meeting and perhaps should not have been includedin a committee report, but they were included to show progresshas been made since our breakthrough in establishing the dis-placement-vibration strain relationship.The task force report is limited to vibration activity measure-

ments and to vibration strain-amplitude relationships and doesnot touch on radial compression stresses caused by tight clampingwith resultant variable end fixities. Also, the report does not coverfretting of conductor elements resulting from improper clampseating which has been observed when fatigue breaks are examined.Further study regarding these characteristics will be necessary beforewe can predict the most suitable climate for a fatigue-free conductor.

It is hoped that new field and laboratory testing will be generatedby the breakthrough in this bending-amplitude-vibration-strainrelationship and that its assimilation will permit us to track downor eliminate each of the seven culprits of the questionnaire.

Manuscript received February 26, 1965.

1966 21

Manuscript received August 5, 1965.


This will only be possible if utilities and public agencies instigatefield testing projects on older and more vulnerable circuits, so thatwe will have country-wide data to program. The end result will becheaper transmission lines through tighter tensions made possiblethrough correctly applied dampers or proper cable seatings.

Members of the Task Force on the Standardization of ConductorVibration Measurements: We are pleased that the discussers con-sider the bending-amplitude method of measuring conductor vibrationto be technically sound and that their experience has shown it tobe a valuable and effective tool for assessing the problem. We areconfident that the general acceptance and use of the method willresult in a more intimate understanding of the many factors whichinfluence conductor fatigue.With respect to the 2-week recording period, we agree with Mr.

Hondulas that this normally provides data representative of anyother time of the year. Recent experience has indicated, however,that in very flat terrain unobstructed by trees or buildings, or inthe vicinity of water masses, such as a large lake or the sea, themaximum wind speed which will induce significant vibration rangesfrom 20 to 30 mi/h compared with 10 to 12 mi/h for normal undulat-ing tree-covered terrain. Since the wind-speed range in many loca-tions may vary considerably depending on the time of the year, a2-week test period may not be sufficient time to obtain representa-tive vibration data in flat unobstructed terrain. Since winds up to10 or 12 mi/h occur relatively frequently in most areas at any time

Manuscript received August 5, 1965.

of the year, 2-week data obtained in undulating tree-covered ormountainous country should be representative of any period.The winter vs. summer vibration measurements for undamped

conductors discussed by Mr. Weldon showed acceptable correlation.Normally we would not expect the winter and summer levels tobe greatly different on damped conductors since the most commonlyused vibration dampers have a damping capacity many times thatof conductors. Only the conductor damping would be expected tochange because of the effect of temperature on tension. Where asignificant difference in level occurs this is most likely to result,as previously discussed, from different wind conditions occurringin the test periods. Examination of the vibration frequency spectrumsfor the two tests would provide some evidence of this. Alternativelyand generally, we would recommend that a reference undampedconductor should be monitored in the same span and at the sametime as the summer and winter measurements are made on thedamped conductor. If it is established that the wind conditionsfor the two test periods were similar while the vibration levels weresignificantly different, then it would appear that the dampers aretemperature sensitive.

It is possible to predict the damped vibration if the undampedamplitudes are known. This requires a knowledge of the vibrationcharacteristics of both the damper and the conductor under con-sideration. Only limited information has been published on theseat this time. Consequently, it is not possible to make general pre-dictions for the wide range of available conductor sizes and operatingconditions. Field tests using the bending-amplitude method would,of course, provide a basis for assessing the vibration performanceof dampers.

Tennessee Valley Authority's 500-kY System-

System Plans and ConsiderationsF. CHAMBERS, FELLOW, IEEE, 0. S. C. HAMMER, FELLOW, IEEE, AND L. EDWARDS, MEMBER, IEEE

Abstract-Insulation requirements for the Tennessee ValleyAuthority's new 500-kV transmission system were found to bedictated by switching surge transient voltages rather than by light-ning surges. Plans and considerations studied by the TennesseeValley Authority in relation to the employment of 500-kV trans-mission are presented as comparative data which might be helpfulto others interested in EHV installations. Descriptions are givenof voltage levels and bundle conductors selected, subconductorarrangements, application of shunt compensation, reactive powersupply, lightning performance, system stability, system grounding,insulation requirements, 500-kV bus arrangements and relaying,and transformer capabilities meeting the needs of 500-kV trans-mission in the TVA service area.

Paper 31 TP 65-43, recommended and approved by the Trans-mission and Distribution Committee of the IEEE Power Group forpresentation at the IEEE Winter Power Meeting, New York, N. Y.,January 31-February 5, 1965. Manuscript submitted October 1,1964; made available for printing July 28, 1965.The authors are with the Tennessee Valley Authority, Chatta-

nooga, Tenn.

INTRODUCTION

BECAUSE OF the relative compactness of its servicearea, TVA found it economical, for some three

decades, to use a maximum transmission system voltage of161 kV. About six or eight years ago, preliminary studiesrevealed that, when total loads reach 12 to 15 million kilo-watts, it would be more economical to employ a higher volt-age in some portions of the system. Further studies indi-cated that the most economical voltage for TVA's purposeswould be 460 kV (which was the designation used at thattime). Refinements of these studies, in accordance with theactual pattern and magnitude of load developments, pre-dicted 1966 as the in-service date for the first 500-kVfacilities.

Contracts were entered into providing that exchangesof power and energy between TVA and the South CentralElectric Companies (SCEC) group would be initiated

22

VOL. PAS-85, NO. 1 JANUARY, 1966

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