Summary: This paper discusses field testsand operating experience on long 275-kv transmission lines. Successful single-pole reclosing depends upon the self-extinc-tion of the secondary arc which persists afterthe interruption of the power arc upon theisolation of the faulted phase. Analysis ofthe test oscillograms showed the secondaryarc to be inherently unstable. Operatingexperience during the 21 months since com-missioning confirms these results as all re-closures have been successful.

THE PURPOSE of the field testsdescribed in this paper was to in-

vestigate the feasibility of applying single-phase reclosing to two long 275-kv linesforming part of the main transmissionsystem of the Electricity Trust of SouthAustralia.A considerable amount of laboratory

and field work has been carried out byother investigators on the behavior oflow-current capacitive arcs following high-current fault arcs.'-12 Indications are thatthere exists a critical secondary arc cur-rent of about 15-20 amperes. For lowervalues, the secondary arc extinguishes ina few cycles, while for higher values, thearc is self -maintaining unless extinguishedby some outside influence such as wind.When one phase of a transmission line

is opened at each end the isolated-phaseconductor still possesses a voltage toground due to the capacitive coupling be-tween itself and the other two lineconductors, and also to ground. Themagnitude of this residual voltage is afunction of the capacitances involvedwhich, in turn, depend upon the physicalconfiguration of the phase conductors. Itfollows that the capacitive current whichwill flow after the interruption of thepower arc is a function of line length.Although usually an electromagnetic

Paper 62-1100, recommended by the AIEE Trans-mission and Distribution Committee and approvedby the AIEE Technical Operations Department forpresentation at the AIEE Summer General Meet-ing, Denver, Colo., June 17-22, 1962. Manuscriptsubmitted March 27, 1962; made available forprinting May 7, 1962.

K. H. MILNE is with The Electricity Trust ofSouth Australia, Adelaide, South Australia.

The author expresses his thanks to the members ofthe staff of The Electricity Trust who assistedin the tests, particularly those in the substation de-partment.

effect also exists, it is normally only ofsecond-order significance and its in-fluence will depend on the position atwhich the fault occurs.

For the lines under test, theoreticalcalculations indicated that the value ofthe electrostaticallyinduced secondary arccurrent would be just below the criticalrange for self-extinction. Thus, themain objective of these tests was to in-vestigate the stability of the secondaryarc.

Extensive field tests have been madeon long high-voltage lines to ascertainthe feasibility of single-pole reclosing.3-7

Port Augusta-Magill Installation

The two single-circuit 275-kv lines onwhich the tests were carried out werebuilt to link the Playford B 240-megawattcoal-burning power station at PortAugusta with Adelaide, a distance ofapproximately 180 miles. The actualtermination is at Magill Substation on theoutskirts of Adelaide. Table I gives thepertinent details of the two circuits whichare located on separate easements. Thescheme has been designed to be stableeven if one line remains out after a fault.For lines operating at these high volt-

ages at least 80%, and more probably90%, of the faults causing outages are of atransitory nature and affect only onephase. In all such instances a successfulreclosure would be possible. Lightningis the prime cause of such, faults, andtheoretical calculations indicated that

the lightning performance of the twolines, which traverse country having anaverage isokeraunic level of 18, could beexpected to be 1.6 and 15.0 outages peryear for the East and West Circuits re-spectively. The first of these figures indi-cates the efficacy of a continuous groundwire, as used on the East Circuit, givinga 30-degree protective angle. On theWest Circuit, ground wires are only usedadjacent to the two terminals, for a dis-tance of 5 miles out of Port Augusta and15 miles out of Magill Substation. Thelonger shielded zone at Magill providesadded protection where the line traverseshilly country prone to lightning.Normal operation of each of the 275-kv

lines is with three single-phase 8-mva(megavolt-ampere) 275-kv shunt reactorsswitched directly onto the line at PortAugusta. Only three tests were con-ducted with the reactors in service.The line circuit breakers are single-

pole air-blast units with eight breaks perpole and of 3,500-mva (synnnetrical)short-circuit rupturing capacity. Pro-tection equipment installed is a 4-zonehigh-speed distance type with power-linecarrier intertrip.

STAGED TESTS

For the tests, the lines were fed radiallyfrom the Magill end and the single-phase-to-ground faults applied at Port Augustaand Magill in turn. The system layoutused for the third series of tests at PortAugusta is shown in Fig. 1. For eachseries of tests, a temporary testing rig waserected in which a standard line suspen-sion string of insulators, 20 10- by 53/4_inch disks, was used and fitted with rodgaps of either 5-foot.3-inch or 10-foot spac-ing between tips. The 10 feet representedthe clearance across the normal suspen-sion insulator string while the 5-foot 3-inch gap approximated the minimumclearance to ground in the terminal switch-yards.

East Circuit West Circuit

Line length, miles .................... 191 .................. 180

Conductor (both circuits) ..........................ACSR* 54/7/0.139 "Moose'Normal span, feet ......................................... 1,450 .................. 1,050Minimum ground clearance at mid-span, feet ..................25 .................. 25

Double at terminalsOverhead ground wires .............................Single continuous 5 miles at Point Augusta

t 15 miles at MagillMaximum protective angle, degrees ..........................30 .................. 30

Transpositions .....................................Two complete ..........Two completeTowers...........................................Steel lattice ............Concrete steel pole piConductor configuration ...... ...................... Triangular ............. HorizontalConductor GMD, feet .......................................30.7 .................. 32.6

Height of conductor above ground at support, feet. Top phase, 90 ...............56

tBottom phases, 66

* Aluminum cable, steel reinforced.

Milnee-Single-Pole Reclosing Tests on 275-Kv Transmission Lines

Single-Pole Reclosing Tests on Long

275-Kv Transmission Lines

K. H. MILNEMEMBER IEEE

Table 1. Details of 275-Kv Lines

658 OCTOIBER 1963

For the first four tests at Port Augusta,the insulator string with rod gaps at-tached was hung vertically from a sec-

tion of overhead buswork and the lowerend was solidly grounded. For the re-

imainder of the tests, at both PortAugusta and Magill, the test string ofinsulators simulated a normal line suspen-

sion point in that it was hung from a

grounded member and the lower endconnected to the live buswork by a shortlength of copper conductor. On alloccasions the test area was shielded withtarpaulins as a precaution against un-desirable wind.

Initiation of the fault was achieved bybridging the rod gap with fine wire andthen switching onto the already energizedline by closing a circuit breaker. Theinfluence on results of the type of wire

MAGILL PT AUGUSTA

EAST WEST

used for arc initiation was investigatedby substituting soft iron wire (no. 21American wire gage) for the tinned copper

fuse wire (no. 24 and 27 American wiregage) used initially. Identical test condi-tions were maintained to obtain thiscomparison.The arc was filmed by high-speed mo-

tion picture cameras in both black-and-white and color film during the first testsat Port Augusta and Magill. Oscillo-graphic records were taken of phasevoltages and currents of the faulted andunfaulted phases. In particular, thesecondary arc voltage and current were

recorded to a suitable scale by usingamplitude limiters to suppress the largerdeflections which had existed before theactual interruption of the main faultitself.

Analysis of Test Results

Twenty-six tests were conducted. Inall but three tests, self-extinction of thesecondary arc followed by successful re-closure occurred. Incorrect adjustmentof the protective relays caused premature3-phase tripping in the first two tests, andin test no. 3.3 the secondary arc per-sisted for the 39 cycles until reclosurewhen the protective equipment initiated a3-phase trip and lockout. A summary ofthe test results is given in Table II, andselected oscillograms in Fig. 2. Re-cords of the secondary'arc current clearlyshow the pulsing effect characteristic of anunstable arc which successively restrikesuntil finally extinguished. This phe-nomenon occurred in varying degrees inall tests. Stages in the development andextinction of the secondary arc are shownin Fig. 3.

Atmospheric conditions during thetests were good except for the first fourtests at Port Augusta which were con-ducted in the evening following a dayof periodic squalls of high wind and rain.For the remainder, conditions were calmand clear, anemometer readings indicatingwind velocities of less than 5 miles perhour within the test area. These calmconditions are evident from photographicrecords, as there appears to have beenlittle or no drift of the arc products apartfrom that attributable to natural convec-tion.

Table II. Summary oF Single-Pole Reclosing Tests on 275-Kv Lines

Fault Reclosing Duration of Recovery 275-KvCircuit Rod-Gap Fault Clearing Dead Secondary Voltage on Shunt Type of W re

Test Under Spacing, Current, Time, Time, Arc Current, Isolated, Reactors for FaultNo. Test Location of Fault Feet-Inches Amperes Cycles* Cycles* Cycles* Phase, Kv in Service Initiation

IlitE 17 . it1.2t ........ West... Port Augusta .......... 5-3. 410.. 20. 10t.. No. CopperH.3 { 15. 26......... 14.01.4 16 26 21.0

2.1 ..9. 225.........8.0 17.32.2 l9 296 8.0 .. 16.312.3 9 26 6.02.4 ........ West.. Magill .................5-3. 980........ 15. 26......... 5.0. 17.8 ........No. Copper2.5 15 25 .........20.52.6 9 ..........925 . 6.0 .. 17.52.7 9. 25. 5.0. 18.4.3. 1 { 22 r 19.7 1 Copper3.2 1 22 5.0 Copper3,3 + | 12 39+ Copper3 .4 ........ INe t Port Augiista............... 5-3 570 ........ 12 39 24. 6 20.......... No ..... Copper3.5 12 ..24.5 Iron3.6 12 17.0 .Iron3.7 12 9.5 Iron3.8 West ..........Port Augusta .10-0 ..570 12 ... 39 . 4.5 20 ..No .Iron3.9 West.. Port Augusta. 10-0. 570. 12......... 39. 4.5. 20.No. Iron3.10 t 4.6)3.11 j 6.3 .. 21.No. Iron3.12 7.43.13 ........ Es......... PortAugusta ..........10-0 ..550. .11. 36. 3.63.14 5.0j ... 30+§.... Yes Iron

3.15 4.0J

* Times on basis of 50 cycles per second.t Tests 1.1 and 1.2 inconclusive due to premature 3-phase tripping.I Unsuccessful reclosure, prolonged secondary arcing.§ Oscillation of recovery voltage with high peak amplitudes.

Milne-Single-Pole Reclosing Tests on 275-Kv Transmission Lines

Fig. 1. System layout for tests

OCTOBER 1963659

Fig. 2. Oscillograms

A-Fault, arc, and recovery voltagesB-Secondary arc current; main fault current distorted by amplitude limiters

In the tests, the ground faults werelocated at either end of unloaded lines,thus involving the electromagnetic aswell as the electrostatic effect. Calcula-tions for the West Circuit indicate anelectromagnetically induced current of1.2 amperes as compared with a 12.9-ampere electrostatically induced current.

Since an arc exhibits nonlinear charac-teristics, the waveform of the secondaryarc current is irregular although the 50-cycle fundamental component predom-inates. Due to the early onset of restrik-ing and the consequent irregular wave-form produced, the magnitude of the 50-cycle component of current was deter-mined for only two tests. Good agree-ment with the theoretical values was ob-tained although a high order of accuracycannot be claimed; the results at bestare only very approximate. The second-ary arc resistance varied between 200and 800 ohms, the lower value holdingsoon after isolation and increasing tillfinal arc extinction.

Duration of the secondary arc variedfrom 1/2 cycle to 3+9 cycles, the latterbeing an unsuccessful reclosure. Asshown in Table II, prolonged secondaryarcing occurred when the fault was appliedat the receiving end of the radially fedline and the arc struck across rod gapsof 5-foot 3-inch separation. Oscillo-grams of such tests show that followingthe initial high-frequency oscillation, thesecondary arc varied from a steady-current condition to one of successive re-

strikes at increasingly higher voltages.In two tests, extinction occurred early inthis restriking period. The final stagewas one of sustained arcing with arcextinction being quite random. In onetest this stage of sustained arcing persistedfor 29 cycles before being interrupted byreclosure. Oscillograms of test no. 3.4,reproduced in Fig. 2, show these threestages of the secondary arc.The rmagnitude of the recovery voltage

on the isolated phase of the West Circuitwas approximately 17 kv for the Magilltests and 20 kv for those at Port Augusta.This increase in recovery voltage at thereceiving end of the radially fed line is dueto the electromagnetic component in-duced by the charging currents in theother two phases. These measured volt-ages agreed well with calculated values.Significantly shorter durations of second-ary arcing were recorded when 10-footrod gaps were used. Hence, the slightincrease in recovery voltage at the re-ceiving end of the line would appearsufficient to prolong, to a marked de-gree, the duration of secondary arcingacross a 5-foot 3-inch rod gap.The methods of arc initiation were com-

pared by substituting soft iron wire forthe previously used copper fuse wire.Excessive ionization when using copperwire for arc initiation has been recognizedby other investigators.8 For an explana-tion of the relative ionization behavior ofthe two materials under such conditions,considerable research into their physical

chemistry is required. Oscillograms oftests 3.4 and 3.6 (Fig. 2) clearly demon-strate the effect of the two arc-initiatingmaterials on the behavior of the secondaryarc. The oscillogram of test 3.4, forwhich copper wire was used, indicates thatthe secondary arc was stable, except forminor restrikes, for a period of some 24cycles. In contrast, test 3.6, with ironwire, shows repeated restriking through-out almost the entire period of secondaryarcing. It would appear that the useof copper wire for arc initiation created,between the rod gaps, an ionized atmos-phere which greatly assisted secondaryarcing. In comparison, iron wire causedlittle or no residual ionization.Three tests on the East Circuit were

conducted with the 275-kv shunt reactorsat Port Augusta in service. Arcing timeswere not noticeably altered but the re-covery voltage on the isolated phaseoscillated widely, being the resultant ofthe 50-cycle induced voltage and thenatural transient voltage of the combinedline-plus-reactor circuit. The peak ampli-tudes of the recovery voltage were con-siderably in excess of 21 kv obtained inthe other tests without the reactors. Un-fortunately, the true magnitude of thepeaks cannot be ascertained, as they werein excess of 30 kv, the "knee point" of thevoltage limiters used in the particularmetering circuit. However, these highvoltages could cause additional restrikingas shown in the oscillogram of test 3.14,Fig. 2. This phenomen has been appre-

Milne-Single-Pole Reclosing Tests on 275-Kv Transmission Lines660 OCTOBER 1963

ciated elsewhere and experiments haveshown that under unfavorable resonaultconditions it might not be possible toquench the arc at all.7

In a total of 24 tests in which single-pole reclosing took place, self-extinctionof the secondary arc occurred in all casesexcept one-when a fault at the receivingend of the radially fed line was initiatedby copper fuse wire across a 5-foot 3-inchrod gap. For the more practical case offlashover across a 10-foot rod gap andwith minimum ionization by using ironwire for arc initiation, the longest re-corded duration of secondary arcing was7.4 cycles.For successful single-phase reclosing,

there must be adequate time between theextinction of the secondary arc and thereclosure for deionization and re-estab-lishment of the dielectric strength betweenthe arc electrodes. A determination ofthe minimum required time was notsought, but 5 cycles proved adequate inone of the tests.

Operating Experience

During the first 21 months of opera-tion of the West Circuit, 13 single-phaseoperations occurred. Lightning was thesuspected cause in each and all reclosureshave been successful. No faults haveoccurred on the East Circuit during the11 months since its commissioning.Thunderstorm activity has been markedlybelow the average isokeraunic level of 18used in the initial estimation of line out-ages. Admitting the uncertain accuracyof drawing conclusions after so limited atime, the outages are of the same orderas predicted.The line-protective equipment has

been set to give an effective reclosing deadtime of 25 cycles. This has been quiteadequate to allow for secondary arcextinction and subsequent deionization.

(A) (B) (C) (D)Fig. 3. Development of secondary arc, test no. 1.3

A-Commencement of secondary drcing after interruption of main fault currentB-Secondary arcing between rod gapsC-Secondary arc fully extendedD-Final extincticn of secondary arc1 less thdn 1 cycle after (C)

Conclusions

The single-pole reclosing tests carriedout on the 275-kv lines have shown:

1. Single-phase reclosing was successfulwith a reclosing dead time of 25 cycles (0.5second).2. Oscillographic records revealed thesecondary arc to be inherently unstable.

3. The secondary arc resistance varied be-tween 200 and 800 ohms.

4. Prolonged secondary arcing is possibleupon the isolation of the faulted phasefollowing a single-phase-to-ground faultacross a 5-foot 3-inch rod gap at the receiv-ing end of 275-kv lines.5. In practice, if flashover occurs across thenormal 10-foot suspension insulator string,self-extinction of the secondary arc can beexpected within a few cycles.

Based on these tests and limited operat-ing experience to date, it is intended tocontinue to apply single-phase reclosingon these 275-kv lines with an effectivedead time of 25 cycles.

References

1. INSULATOR FLASEIOVER DE-IONIZATION TIMESAS A FACTOR IN APPLYING HIGH SPEED RECLOSINGCIRcUIT BREAKERS, A. C. Boisseau, B. W. Wyman,W. F. Skeats. Paper no. 135, CIGRE, Paris,France, 1950.

2. RESIDUAL CURRENTS AND VOLTAGES WITHSINGLE POLE RAPID RECLOSING, A. Amstutz.The Brown Boveri Review, Baden, Switzerland,July/Aug. 1948.

3. SINGLE POLE RECLOSING-RELAYING PROB-

LEMS AND ARC EXTINCTION TIMES, W. P. Dobson,V. V. Mason. Paper no. 316, CIGRE, 1952.

4. SINGLE POLE RECLOSING-FIELD TESTS INSWEDEN ON A 220 KV 480 KM TRANSMISSION

LINE. Report to Study Committee No. 13,

CIGRE, May 1953.

5. DOnS THE LENGTH OF LINE LIMIT THE APPLICA-TION OF SINGLE PHASE RECLOSING IN VERY HIGH

VOLTAGE TRANSMISSION SYSTEMS? Cabanes,Dietsch, Divan. Paper no. 14 , CIGRE, 1954.

6. SINGLE POLE RECLOSING-FIELD TESTS IN

SWEDEN ON A 380 KV 415 KM TRANSMISSION LINE.

Report to Study Committee No. 13, CIGRE,May 1954.

7. MINIMUM TIME OF AUTOMATIC RECLOSING,

A. S. Maikopar. Elektrichestvo, Gosenergoizdat,Moscow, USSR, no. 6, 1959.

8. STAGED FAULT TESTS OF RELAYING AND

STABILITY ON KANSAs-NEBRASKA 270-MILE 154-KV INTERCONNECTION, C. W. Minard, R. B.

Gow, W. A. Wolfe, E. A. Swanson. AIEE Trans-actions, vol. 62, 1943, pp. 358-67.

Experiments with Galloping SpansJAMES J. RATKOWSKI

MEMBER IEEE

H IGH-AMPLITUDE low-frequencyvibration of transmission lines,

"galloping," is a recognized problemwhich has been studied for a number ofyears. This phenomenon occurs mostoften when the wires are coated with an

Summary: The energy imparted to agalloping span by the wind and the energydissipated by frictional sources in the spanare investigated, and a short-span experi-mental line fitted with air foils is used toverify the method of calculating the windand friction energies. The experience

gained from various test spans is presented.The input energy and the energy dissipationof a full-scale span is investigated for ahypothetical conductor cross section. Adiscussion of the role that torsional motionplays in galloping is also included in thispaper.

Paper 62-62, recommended by the AIEE Trans-mission and Distribution Committee and approvedby the AIEE Technical Operations Departmentfor presentation at the AIEE Winter GeneralMeeting, New York, N. Y., January 28-February2, 1962. Manuscript submitted October 16, 1961;made available for printing July 11, 1962.JAMES J. RATKOWSKI is with the CommonwealthEdison Company, Chicago, Ill.

RatOowski-Experiments with Galloping SpansOCTOIBER 1963 661