IEEE Transactions on Power Apparatus and Systems, Vol. PAS-104, No. 9, September 1985

DEVELOPMENT OF A 500kV AIRBLAST HVDC CIRCUIT BREAKER

B. Bachmann G. MautheMember IEEE

E. Ruoss H.P.LipsSenior Member IEEE Senior Member,IEEE

Brown Boveri & Co.Zurich, Switzerland

J. Porter, Senior Member IEEEElectric Power Research Institute

Washington D.C. 20036

Abstract - The concept of a new HVDC circuit-breaker for 500 kV and its operating principle areexplained. The interruption of the direct current isbased on a "passive" commutation circuit.

Laboratory tests with an experimental breaker anda-prototype breaker were performed. The prototype wasfinally tested in the field on the Pacific Intertie.

INTRODUCTION

A major development in power systems in the lasttwo decades has been the growth of HVDC transmissionsystems in various parts of the world. These systemsare exclusively point-to-point links for thetransmission of energy. Additional HVDC systems,including interconnections of existing systems, arepresently studied or planned. This represents achange from the present two-terminal layouts tomulti-terminal arrangements.

Up to the present, the two-terminal networks havebeen operated without any HVDC circuit-breakers. Theuse of such breakers in multi-terminal operation wouldprovide major advantages, both for switching opera-tions and for fault clearing.

The use of HVDC circuit-breakers has beendiscussed for some time and various proposals fortheir design and implementation have been published[1]. Except for the use of low voltage dc breakers as"metallic return-transfer breakers" in some cases, noreally practical solutions for HVDC breakers have asyet been found [3,4].

Advances in the technology of energy absorptionelements, such as metal-oxide (MO) resistors, openedup new opportunities for the development of an HVDCbreaker that can be used not only for operationalswitching, but also for rapid fault clearing.

The development of a new HVDC circuit-breaker for500 kV, which has been tested on the Pacific Intertie,was carried out by Brown Boveri Corporation (BBC) inclose collaboration with the Electric Power ResearchInstitute (EPRI) and the Bonneville Power Administra-tion (BPA).

85 WM 251-4 A paper recommended and approvedby the IEEE Switchgear Committee of the IEEE PowerEngineering Society for presentation at the IEEE/PES 1985 Winter Meeting, New York, New York,February 3 - 8, 1985. Manuscript submittedSeptember 19, 1984; made available for printingDecember 12, 1984.

J. Vithayathil, Fellow IEEEBonneville Power Administration

Portland, Oregon

CONCEPT OF THE HVDC BREAKER SYSTEM

Concepts for Interruption of Direct Current

The basic circuit used for interrupting directcurrent is illustrated in Fig. 1. This circuitconsists of three main components:

1. the current-carrying commutation switch2. the commutation circuit3. the energy absorber circuit

0 -1~ 0

COMMUTATION SWITCH

COMMUTATION CIRCUIT

ENERGY ABSORBER

r3

.-

FIG. IGENERAL PRINCIPLE OF HVDC CIRCUIT BREAKER

The commutation switch is the main contact elementof the HVDC breaker. When switching, the current isfirst made to commutate from the commutation switchinto the commutation circuit. Then the current istransferred to the energy absorber for dissipation ofthe remaining energy stored in the dc circuit.

In principle, a distinction can be made betweentwo fundamentally different kinds of commutationcircuits: "active" and "passive" circuits. In bothcircuits suitable measures have to be taken to ensurethat, when the commutation switch is opened, thecurrent in this switch is reduced to zero, even ifonly for a short time. The current is thusinterrupted and forced to flow into the commutationcircuit and finally into the energy absorber circuit.

In the "active" commutation circuit devices suchas auxiliary switches, spark-gaps and/or prechargedcapacitators have to come into action at theappropriate moment. In the "passive" commutationcircuit, on the other hand, such devices areunnecessary. The conditions for interruption of thecurrent in the commutation switch are created solelyby passive elements in parallel with the switch and bythe properties of the switch itself. There is no needfor additional moving, controlled or triggeredelements.

0018-9510/85/0009-2460$01.00©1985 IEEE

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The Principle Selected: Passive Commutation Circuit

In the selected passive commutation circuit, anL-C series resonant circuit is connected in parallelwith the commutation switch, as shown in Fig. 2.

FIG. 2PRINCIPLE OF THE "PASSIVE" COMMUTATION CIRCUIT

The differential equation of this commutationcircuit can be expressed as follows:

d2i du di2 arc 2 1L t2 + +- i2 =0

dt di1 dt C

Since uarc decreases with increasing current il,duarc < o

dilIf the actual "stray" resistance of the commuta-

tion circuit - that of the inductor L and theconnections - is smalll, an oscillation initiated inthe commutation circuit will not be damped, but wouldpossess an amplitude that increases with time. Sincethe arc voltage in the commutation switch is neverstable, but varies due to the inherent movement of thearc and the blast to which the arc is subjected, anoscillation of this kind can be initiated by theseshort-time "disturbance functions."" With suitablemagnitude and characteristic of the arc voltage, theamplitude of the current in the commutation circuitattains the value Io, with the result that thecurrent il becomes zero for a short time.

When the current is zero, the commutation switchquenches the arc, i.e., the current i1 isinterrupted. The current Io continues to flow fromthe network (see Fig. 3). This charges up thecapacitance C. The voltage that builds up across thiscapacitance is limited by the MO energy absorber.

MO ENERGY ABSORBER

FIG. 3MODULE OF THE HVDC BREAKER

Ls = System inductanceIo = Nominal currentSo = Direct current modified by the breakeril,i2,i, see Fig. 4.

The shape of the voltages and currents associatedwith this process with respect to time is illustratedby Fig. 4. If a short circuit occurs on the HVDCtransmission line, the fault current is reducedrapidly to the level of the rated current by theconverter control system. Consequently, either therated current or a fault current with the samemagnitude as the rated current has to be interrupted.

Contact Separation

Fig. 4aUabsorber--,LS

UDC

\Ur i-o. Fig. 4bF > ~~~~~~~~~Fig. 4c|\ >~~~0 Fig. 4d

FIG. 4 CURRENT INTERRUPTION BY THE HVDCCIRCUIT-BREAKER ACCORDING TO THE PRINCIPLEIN FIG. 3

tO: Contact separation of commutation switchti: Interruption of current ii in the

commutation switchtc: Commutation timeUDC: System voltage

At to (Fig. 4a) the contacts of the commutationswitch separate. The characteristic of the arc,together with the commutation circuit, results in thecurrent oscillation shown. At t1 the current i1through the switch is interrupted. Across thecommutation circuit the voltage rises due to theimpressed current Io, until it reaches the limitingvalue ("clipping voltage") of the non-linear MO energyabsorber (see Fig. 4b). This absorber voltage ishigher than the system voltage UDC and now acts ascounter-voltage to reduce the system current Io tozero (see Fib. 4c).

The rate of rise of the voltageabsorber- circuit until the "clippingreached, corresponding to the r.r.r.v.commutation switch, is (o/C)O.

across thevoltage" isacross the

When the absorber clipping voltage is reached, thecurrent Io flows into the absorber circuit, so thatthe remaining energy contained in- the systeminductance is now dissipated in the absorber, bringingthe current io to zero (see Fig. 4c). When thecurrent io has dropped to zero, the resistance ofthe MO absorber again becomes very high and the systemvoltage across the breaker is re-established.

i3

L0 0 01 v

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Practical Application

The phenonema described above indicate thecriteria for practical application. If a commutationswitch having the right arc characteristic isavailable, the application of the simple passivecommutation circuit is possible. A decisive advantageof such a circuit for practical applications is thatonly well-known components are employed. In terms ofarc voltage magnitude and characteristics a standardairblast breaker is a suitable candidate as a commuta-

tion switch. No additional moving parts are needed inorder to initiate the commutation process. Allelements in the commutation circuit have reasonablevalues.

The connection of several modules in series, asshown in Fig. 3, permits adaptation to different dcsystem voltages. For the 500 kV breaker, forinstance, four such modules were arranged in series,as described later.

MAIN DATA OF PROTOTYPE BREAKER

The following data were specified for the prototypeHVDC circuit-breaker:

Nominal system voltage 500 kV dcBreaker "counter voltage" 700 kV dcContinuous and interrupting current 2200 A dcSIL, terminal to terminal 1175 kV

terminal to ground 1175 kVBIL 1550 kVEnergy absorption capacity of absorber 10 MJMaximum time from trip to commutate 35 ms

DEVELOPMENT TESTS AND ASSOCIATED INVESTIGATIONS

Theoretical Investigation of the Commutating Process

A breaker test arrangement was set up in thelaboratory to determine the electrical values of thecommutating circuit elements, to dimension the energyabsorber units, and to make final modifications- to thecommutation switch. Parallel to the laboratory tests,computer calculations were performed, during which theswitching arc was simulated with an arc modelaccording to the Mayr equation. The method isdescribed in [6].

Calculations were made varying the parameters C, L andR of the commutation circuit, as well as the current10. The tests performed in the laboratory, partlyas a result of the computer calculations exhibitedgood agreement with the simulations. In this mannerit is possible to determine the optimal dimensions.Fig. 5 shows a computed oscillogram and Fig. 6 thecorresponding oscillogram obtained during laboratorytests. The development of current oscillations insteps, as seen in Figs. 5 and 6, is attributed tosudden changes in the arc geometry and arc voltage [6].

Laboratory Development Tests

The principle illustrated in Fig. 3 and 4 wastested in the laboratory with a circuit as illustratedin Fig. 7. From a rectifier a) the current to beswitched was fed at constant voltage (a few kV)through a reactor of 0.5 H to the closed dc circuitbreaker, or one of its modules. During theinterruption the inductance of 0.5 H acts as a currentsource. In th-is way it was possible to fully test thestresses imposed on the HVDC breaker module. Duringthe test on two breaker modules in series thecommutation process was correctly simulated. However,the voltage across the two modules was limited to

FIG. 5 CALCULATED CURRENT COMMUTATION WITHTHE ZPASSIVE' COMMUTATION CIRCUIT, USING THEMAYR ARC MODEL EQUIVALENT

Uarc = Arc voltageI i = Current In the Commutation Switch

arc

i1=

Fig. 6 MEASURED CURREN C04MUTATICON WITHSAME CCMMUTATION CIRCUIT AS IN FIG. 5

a)0.5 HVDC BREAKER

I I IQ MODULE

b)

FIG. 7 LABORATORY TEST CIRCUIT FOR TESTINGONE AND TWO MODULES OF THE HVDC BREAKER

a) Rectifier operating at 3 to 4 kVb) HVDC test breaker or prototype breaker

about 200 kV by adjusting the absorber clipping level,since the 0.5 H reactor was only dimensioned for avoltage of 250 kV.

Fig. 8 shows the results of interrupting tests withone module, i.e., one interrupter of the commutationswitch with its LC circuit and energy absorber. Itcan be clearly seen that the commutation time tc isdependent on the magnitude of the current to beswitched.

tcms

20I

10

0

OX X

X 0

x0

O xo xo ox x

I I I I I I I

1 2 3 4 5 6 7

X x X0 0 X X o o

0 X

ox

I II In

I I I I 10.5 1.0 1.5 2.0 2.5 kA

FIG. 8 COMMUTATION TIME tC OF ONE MODULEVS. DIRECT CURRENT 10 TO BE INTERRUPTED

Fig. 9 shows the test results of two breakermodules connected in series. Here the commutationtime tc is shown for a group of tests during which a

direct current of 2400 A was interrupted. From theresults it is quite clear that the total commutationtime (11 to 14 ms) is shorter than that for the testson a single module. The two modules are electricallycoupled, so that the maXimum difference between theircommutation times during an operation amounted only toabout 1.5 ms.

Fig. 10 also shows the oscillograms obtainedduring a group of tests witkh two breaker modules inseries, where 2400 A was interrupted. Fig. lOa showsthe current through the commutation switch. Thefrequency of the oscillation is approximately! 7 kHz.Fig. lOb shows the voltage across one and bothmodules, from which it can be seen that there is very

little difference between the moments of commutation.This is important because it influences the thermalcapacity required by the energy absorbers.

It is also possible to apply circuit breakermodules which consist of more than one break. Testshave been carried out with a module consisting of twobreaks and twice the elements bf the basic commutationcircuit in series (see Fig. 11). For such a connec-tion the resulting capacitance of the commutationcircuit is reduced to half the value while theresulting inductance is doubled. Fig. llb shows themeasured commutation time tc obtained duringlaboratory tests with a module in the two-breakconfiguration. These tests prove that such anarrangement is feasible. An advantage is that thedispersion in commutation time between two modules asshown in Fig. 9 could be avoided. The longercommutation times observed in Fig. 11 compared to

FIG. 9 COMMUTATION TIME tc OF TWO MODULESIN SERIES DURING A NUMBER OF INTERRUPTIONSOF A CURRENT lo = 2400

x Commutation time of module 1o Commutation time of module 2

e~

a).

b)

Fig.10 Commutation test with two breaker modules inseries(a) Current oscillation in one of the two modules(b) Voltage across one module (uipper trace) and the

two modules (lower trace)

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tcms

20-

10-

l'O

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C L C L C L C ~L

(a)

LAYOUT OF ThE PROTOTYPE AND PROTOTYPE TESTS

Fig. 12 shows the conceptual view of the completeHVDC breaker for 500 kV (Fig. 12a) and its circuitdiagram (Fig. 12b). One pole of a standard 500 kVairblast circuit-breaker, type DLF, is used as thecommutation switch (1). The energy absorber units (2)mounted on porcelain columns (T) are connected inparallel with each interrupter unit of the commutationswitch. The commutation circuit consists of fourcapacitor banks (4) rated 5 microfarads each and fourair-core inductors rated 100 microhenries which areinsulated from ground by porcelain columns (6). Thecommutation switch is equipped with closing resistors(7) to limit line switching overvoltages.

* 0

10I~~~I- -

1.0 1.5 2.0 2.5 kA

(b)

FIG. 11: a) DIAGRAM OF 500 kV HVDC CIRCUIT

BREAKER WITH: MODIFIED MODULES CONSISTING

OF TWO BREAKS OF THE COMMUTATION SWITCH.

b) COMMUTATION TIME tc OF ONEMODULE ACCORDING FIG. a) VS DIRECT CURRENT

10 TO BE INTERRUPTED.

those in Fig. 8 and 9 is attributed to the laboratoryarrangement not being optimal during these tests. Thefield tests showed the breaker performance is similarto that of Fig. 9 [7].

As shown in Fig. 8, the commutation times are very

short for low currents, i.e., commutation takes placewhen the contacts in the commutation switch are only a

short distance apart. Under certain circumstancesthis can lead to reignition in the, switch during therise of the voltage across the commutation capacitor.This reignition causes the capacitor to dischargethrough the commutation inductor, thus beginningan-other commutation process. Successful completion ofcommutation- would follow with increased separation ofbreaker contacts. The entire phenomenon takes placewithin the commutation circuit and has no significanteffect on the power system.

The laboratory tests confirmed that the selectedcommutation principle can be employed for HVDCcircuit-breakers and, at the same time, yieldedparameters for dimensioning the commutation circuit.

C L C L C L

(b)

FIG. 12(a) CONCEPiUAL VIEW AND (b) CIRCUIT

DIAGRAM OF THE 500 kV CIRCUIT-BREAKER

Commutation Switch (1) (see Fig. 12)

One pole of an ac 550 kV air-blast circuit-breaker, type DLF, consisting of four interrupters in

series and equipped with 400 ohm closing resistors isused as the commutation switch [8,9]. The arc voltagecharacteristic of these commutation switchinterrupters is an essential feature in generating the

current oscillation to obtain current zeros.

The porcelain insulators used for the prototypebreaker are of conventional ac type. Extra longinsulators for the interrupters are used to provide a

sufficient creepage distance across the open switchfor the specified time the breaker is subjected to thefull voltage in open position. Also the insulation toground is ensured by normal porcelain used for acbreakers. Special dc porcelain insulators can beemployed if necessary without any difficulties.

tcms I

20 -

10 -

0.5a)

a

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Energy Absorber (2)

Eight absorber units are installed on the completebreaker- 2 parallel units in each module. Four stacksof MO discs are connected in parallel in each unit.The complete energy absorber can dissipate at least10 MJ of energy. This enables the breaker to carryout several operations or switching cycles before theenergy dissipation limit due to excessive heatgeneration is reached. In designing the energyabsorber an increase in rating due to the smalldispersion of the commutation times between theindividual breaker modules is also taken into account.

Capacitor Bank (4)

The capacitors used in one module consist of fivecans in series and five such groups in parallel togive 5 microfarads per module. The "all filmtechnology" for the roll type capacitors is employedusing pure plastic films instead of paper. Thisdesign ensures the necessary mechanical strength whenthe capacitors are stressed by an inrush current.Discharge resistors will discharge the bank to lessthan 50 volts within 4 to 5 minutes.

Inductor (5)

The prototype inductor of the commutation circuitis a single-layer, dry-insulated, air-core cylindricalcoil. It consists of a cylindrical glass fiber bodyon which a copper tape is wound and insulated withglass-mica material. Both coil ends are shielded bycorona rings. The inductance value of the coil is inthe order of 100 microhenries.

Multiple Module Application

For the 500 kV system voltage level an air-blastcommutation switch with four interrupters in series,as descrlbed above, has to be employed. Thecommutation circuit can be arranged in various ways.

a) "4-module" -- configuration as shown in Fig.12: In principle the current oscillation in eachmodule takes place independently. But as it was shownin Fig. 9, there is coupling between the modules whichkeeps the dispersion in commutation times between theindividual commutation modules to less than 2 ms.This dispersion leads to an increase in the power tothe energy absorber of the module which commutatesfirst. Therefore, the energy absorbers have to bedimensioned to account for this effect.

b) "2-module" - configuration: Two interruptersof the commutation switch are combined into onecommutation circuit (see Fig. lla). The advantages ofthis arrangement is that there are only two modulesinstead of four. Within one module, which containstwo breaks of the commutation switch, no dispersion ofthe commutation time occurs. Therefore, it is likelythat the dispersion of the commutation times for thetotal breaker would be smaller.

c) "1-modulei' - configuration: In this case thecapacitors and inductors are connected across all fourbreaks in series. There is only one commutationcircuit. Therefore, there is no dispersion incommutation times and no single energy absorber unitis stressed higher than the others. Thisconfiguration -has not yet been tested in thelaboratory, but computer simulation has shown, thatsuch an arrangement would also operate successfully.

With the test circuit shown in Fig. 7, thefull-scale prototype breaker consisting of fourbreaker modules was tested. Fig. 13 shows theprototype breaker in the test lahnratonrv

Fig. 13 500 kVTHE TEST LABORATORY

DC. PROTOTYPE CIRCUIT-BREAKER IN

FIELD TESTS

In February 1984, the prototype breaker was testedat the Celilo Station of the Pacific Intertie. Fig.14 shows the prototype breaker with four modules inseries, as installed in Celilo substation. Visiblefrom left to right are: The commutation switch, theMO energy absorber, the inductor and the capacitorbank of the commutation circuit.

Tests were made at 400 kV which includedswitching, load breaking and fault clearing.currents ranged from 500 to 2000 amps.commutation times ranged from 2.5 to about 12 ms.tests were successful. Details of these testspresented in Reference 7.

lineTestTheAllare

Fig. 14 500 kV HVDC CIRCUIT-BREAKER IN CELILOSTATION OF THE PACIFIC INTERTIE

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CONCLUSIONS

The development tests on the 500 kV HVDC circuit-breaker proved that a current of up to 2500 A can

be interrupted. by taking advantage of the arccharacteristic of an airblast commutation switch.

- The advantage of this principle is its simplicity.No auxiliary switches or electrically activesourcei are required.

- The development tests revealed that there ispotential for even higher breaking currents.

- Actual field tests with interrupted currents up to2000 A, at 400 kV carried out on the Pacific HVDCIntertie deMonstrate the practical application ofthe principle of this HVDC breaker.

- This HVDC breaker arrangement can be adapted tosuit other dc system voltages, as it is of modulardesign.

REFERENCES

[1] CIGRE Study. Committee 13: .,"Application of HVDCCircuit-Breakers," Electra No. 31, 1973

[2] CIGFRE Working Group 13.03: "The Metallic ReturnTransfer Breaker in HVDC Transmission," ElectraNo. 68, 1980

[3] A.L. Courts, J.J. Vithayathil, N.G. Hingorani,J.W. Porter, 3. Gorman, C.W. Kimblin. "A New DCBreaker Used as Metallic Return Transfer Breaker,"IEEE Transactions, PAS, Vol. 101, No. 10, 1982

[4] J.J. Vithayathil, "HVDC Breakers ard itsApplication," Proceedings of the InternationalSymposium on HVDC Technology, Rio de Janeiro,Brazil, March 20-25, 1983

[5] J.P. Bowles, L."Specificatioh ofDifferent System13-09, 1976

Vaughan, N.G. Hingorani:HVDC Circuit-Breakers for

Applications," CIGRE Report

[6] K. Ragaller, -A.. Plessl, W. Hermann, W. Egli:"Calculation Methods for the Arc Quenching Systemof Gas Circuit-Breakers," CIGRE Report 13-03, 1984

[7] J.J. Vithayathil, Al Courts, W.G. Peterson, N.G.Hingorani, S. Nilsson, J.W. Porter, "HVDC CircuitBreaker Development and Field Tests," Paper to bepresented at IEEE PES Winter Power Meeting, 1985

[8] E. Bross, H. Schubert: "The DLF Range of HighVoltage Airblast Circuit-Breakers; Design,Performance, Applications," Brown Boveri Review65, 1978

-[9] A. Eidinger, G. Koppl: "Type DLF Airblast CircuitBreakers," Brown Boveri Review 54, 1967 (12)

DiscussionThomas F. Garrity (Chas. T. Main, Inc., Boston, MA): The authors areto be commended for the significant step forward in dc breaker develop-ment which they have presented in this paper. There are two areas ofgeneral comments from the authors which are solicited.

(1) The successful application of airblast interrupting technologyclearly represents the use of state-of-the art techniques. With theincreasing world-wide trend toward SF6 technology for circuitbreakers, what is the prognosis for continued availability of airblast interrupters for dc breakers?

(2) With the expected increase in current interruption requirementsfor dc circuit breakers of the future, would the authors commenton the requirements for test facilities to demonstrate satisfactorybreaker design tests?

Manuscript received February 25, 1985

Robert JMtten (Darmstadt, Germany): Invited by the chairman with whomI had contact as a member of CIGRE WG 14-02, Control of HVDCSystems, while he convened a WG on HVDC breakers, I would like tocomment on some of the statements made in the discussion and in thepapers which were presented at this session.

In a CIGRE-REPORT of 1980 on the state of the art in the controlof multiterminal systems there is a rather lengthy discussion on dcbreakers, especially a paragraph on line breaker action in fault cases,which still is true and worth reading. I am pleased with the paper 85WM 216-7 presented at the HVDC session by aWG of IEEE which bringsthe issue up to date on the basis of existing projects.One point of the earlier mentioned paper, however, has been lost. It

has been outlined there that in a meshed system dc breakers are suitableto clear a faulty dc line without changing the power flow pattern butthe speed of the selection of the faulted line with dc is a problem yetto be solved.

I do not agree with the statement made in this discussion that thereis much to be gained by fast dc breakers in stability improvement afterfaults. The current control is able to reduce the current to zero within10 ms to 20ms, and an effort to do it faster by a breaker would be cost-ly for very obvious reasons.Theneed for dc breakers increases with the complexity of the multiter-

minal system, and with manysubstations, taps, branch-offs, it will notbe tolerable to stop the whole system for every switching operation, noteven for a very short time. While in the early stages of HVDC it wasgratifying that no dc breaker was needed, the time has now arrived withprojects for more extended multiterminal systems.

Manuscript received February 28, 1985

B. Bachmann, G. Mauthe, E. Ruoss, H. P. Lips, J. Porter, and J.Vithayathil: We thank Mr. Garrity and Professor Jtftten for their in-terest anl comments. Since Professor Jotten's comments are identicalto those hemade with reference to the companion paper, "HVDC Cir-cuit Breaker Development and Field Tests", our response to those com-ments is includedin the closure of that paper.As to Mr. Garrity's questions, we would like to comment as follows:1. The matter of continued availability of air blast interrupters has

been studied prior to starting the development program. Thistechnology will continue to have a market in ac transmission forspecial switching duties and in adverse cliniatic conditions.Therefore, it will also be available for dc breakers.

2. With current interruption requirements increasing above approx-imately 4000 to 6000 amperes, it may be necessary to revert to alter-native circuits for design testing, such as low-frequency short-circuitgenerators or synthetic circuits in case the available dc source isnot adequate to use the test circuit described in the paper. The pro-blem is eased by the fact that the breaker is of modular design andonly individual modules are needed for design tests once the cor-relation between single modules and full-size breaker has beenconflrmed.

Manuscript received April 9, 1985