AC High Voltage Circuit Breakers - Institute of Electrical ...

1 Denis DufournetIEEE FellowConsultantSathonay-Camp (France)AC high - Voltage Circuit BreakersEverything you wanted to know about ac high - Voltage Circuit Breakers but were afraid to askIEEE Switchgear CommitteePortland (Maine, USA), October 20171980198519891991199820042010 GRID SOLUTIONS40 Years of Experience in HV Circuit Breakers19772015 high - Voltage Circuit Phenomena in HV Circuit Extinction Related to high - Voltage Circuit 1 on TRVA nnex 2 on New Test Procedure T100aAnnex 3 on Transformer Limited high - Voltage Circuit Phenomena in HV Circuit Extinction Related to high - Voltage Circuit 1 on TRVA nnex 2 on New Test Procedure T100aAnnex 3 on Transformer Limited FaultsHigh- Voltage Circuit BreakerDefinitionA mechanical switching device, capable of making, carrying and breaking currents under normal Circuit conditionsand making, Circuit ,smallinductivecurrents, following is required from a Circuit breaker : In the closed position it must be a good conductor; In the open position it must behave as a good isolator between system parts.

2 It must be able to change from the closed to open position in a very short period of time (typically in less than second); It does not cause overvoltages during switching; It is reliable in its interrupting chamber has-Internal Voltage withstand in SF6-External Voltage withstand in airHV Circuit breaker -TypeAIS SF6 Circuit BreakerInterrupting chamber in open positionInsulatorAIS: Air Insulated SwitchgearExample of Medium Voltage Circuit breakerHV Circuit breaker -TypeAIS SF6 Circuit BreakerA: Interrupting chamberB: Insulating columnC: Upper mechanismD: Tripping springE: Closing springF: Control cabinetG: SF6monitoringH: Lower mechanismL: RodHV Circuit breaker -TypeExamples of HV Circuit breaker operatedsingle-phaseAIS SF6 Circuit : Interrupting chamberB: FrameC: Rotating rodD: Tripping springE: Closing springF: Control cabinetG: SF6monitoringHV Circuit breaker -TypeExample of HV Circuit breaker operated three-phaseFXT9 Ur= kVIsc = 25 kAAIS SF6 Circuit BreakerFX 800kV 50kA4 chambers in series per poleModular range with vertical units (one mechanism per chamber)Closing resistorsGrading capacitorsHV Circuit breaker -TypeAIS SF6 Circuit BreakerHV Circuit breaker -TypeAIS SF6 Circuit BreakerInterrupting chambersInsulating columnOperating mechanism(one operates two chambers)800 kV Circuit - breaker in RussiaGL315(D) 300 kV362 kV420 kVGL316(D) 2 XGL317(D)=GL318(D)GL317(D)550 kVGL314 245 kV800 KVHV Circuit Breakers -TypeAIS HV SF6 Circuit BreakersExample of Circuit breaker rangeCircuit breaker with several chambers in series per pole Open Circuit - breaker .

3 Voltage distribution is done by Grading capacitors, or RingsHV Circuit breaker -TypeAIS SF6 Circuit BreakerColors illustrate the Voltage distribution calculated by 3D simulationHV Circuit breaker -TypeVoltage withstand of the interrupting chamber (between contacts and to ground) is fully in SF61: Circuit breaker interrupting chamber2 Circuit breaker operating mechanismGIS Circuit BreakerGIS: Gas Insulated SwitchgearGIS 145 kVHV Circuit breaker -TypeGIS Circuit BreakerGIS 420 kVInterrupting chambersOperating mechanismHV Circuit breaker -TypeGIS Circuit BreakerGIS 420 kVHV Circuit breaker -TypeGIS Circuit BreakerSome advantages of GIS reduced size, not sensitive to environmental conditions, safety (active parts are in an enclosure at ground potential), no perturbation to surroundings, good seismic withstand. For voltages 145 kV, the more economical solution is to have the 3poles in the same ratings for a single-break GIS Circuit breaker420 kV 63 kA with standard design of spring operated mechanism,550 kV 63 kA with hydraulic Circuit breaker -TypeGIS Circuit BreakerDT 245 kV 63 kABushingCurrent transformerInterrupting chamberOperating mechanismHV Circuit breaker -TypeDead Tank Circuit BreakerVoltage withstand of the interrupting chamber (between contacts and to ground) is fully in SF6HV Circuit breaker -TypeDead Tank Circuit BreakerCircuit breaker with several chambers in series per poleVoltage distribution by grading capacitorsHV Circuit breaker -TypeDead Tank Circuit BreakerDead Tank Circuit breaker 550 kVwith grading capacitorsHybrid switchgear (Compact switchgear assembly) Itisacombinationofopen-type(AIS)andmetal -enclosedequipment(GIS).

4 Hybridswitchgearallowstoreducethesizeofs ubstationsandtocombinetheadvantagesofAIS andGIS. SpecificIECstandard:IEC62271-205. CircuitbreakerisofGISorDeadtanktype Dependingonthecapacitanceoftheliaisontoo verheadlines, Circuit breaker -TypeExamples of hybrid switchgear Compact switchgear assemblyHV Circuit breaker -TypeExample of hybrid switchgear (HGIS) 550 kVCircuit breakerDisconnectorBushingHV Circuit breaker -TypeGenerator Circuit BreakerGenerator Circuit Breakers are located between a generator and the step-up transformer. They are generally used with generators of high power (100 MVA to 1800 MVA) in order to protect them safely, rapidly and in an economical must be able to carry high continuous currents (6300 A to 40000 A),and they must have a high short- Circuit breaking current capability (63 kA to 275 kA).HV Circuit breaker -TypeHV Circuit breaker -TypeGenerator Circuit BreakerCircuit breaker located between a generator and the step-up transformer.

5 FKG2 kV 63 kAHV Circuit breaker -TypeGenerator Circuit BreakerThree-phase operation by spring mechanismStandard IEC/IEEE 62271-37-013 (2015)HV Circuit breaker -TypeGenerator Circuit BreakerFKGA8 Generator Circuit breaker Isc= 210 kA Ur= 33 kVSF6circuit breakerDesigned for Power Plants from 700 to 1,500 MWIt is equipped with a spring-operated mechanism per ,000 A nominal current with natural cooling and up to 40,000 A nominal current with IPB forced air : Isolated phase bus ducts Earthing switchDisconnectorVoltage transformerCurrent transformerView portsInterrupting chamberSurge arresterCapacitorGenerator Circuit breaker with associate equipmentHV Circuit breaker -TypeCircuit Breakers must function properly in the following normal service conditions: ambient temperature must not exceed 40 Cand the average value, measured during 24h, does not exceed 35 C; minimum ambient temperature is not less than -25 Caccording to IEC 62271-1, and -30 Caccording to IEEE Other values of minimum ambient temperature can be specified in particular cases, such as -40 C, -50 Cin some countries such as Canada or even -60 Cin Circuit breaker Service ConditionsTemperature in service / SF6pressureDiagram SF6 Pressure Density TemperatureConsideringafillingpressureof 7,5bar(g).

6 At20 C,liquefactionoccurswhentemperaturereach es-25 C, (g)at20 in service / SF6pressureHV Circuit breaker Service ConditionsPressurescale Theminimum(lock-out)pressure(at20 C) Alarmpressureis4%higherthantheminimumpre ssure. Fillingpressureisapproximately10% Circuit breaker Service ConditionsTemperature in service / SF6pressureGasmixture Inthecaseofverylowambienttemperatures( C),itisdifficulttoobtaintherequiredperfo rmanceswithpureSF6. Inthesecasesgasmixturescanbeusedwiththea cceptablepressureofSF6andtheadditionofan othergas(SF6-CF4,SF6-N2). Anothersolutionistouseheatingbelts(forDe adtankcircuitbreakers).HV Circuit breaker Service ConditionsTemperature in service / SF6pressureIn the case of SF6-CF4and SF6-N2gas mixtures, Voltage withstand as function of the percentage of SF6. HV Circuit breaker Service ConditionsDielectric Strength of SF6 Gas high - Voltage Circuit Phenomena in HV Circuit Extinction Related to high - Voltage Circuit 1 on TRVA nnex 2 on New Test Procedure T100aAnnex 3 on Transformer Limited Faults Electrical insulation high dielectric strength, approx.

7 Times that of air (depending on density) Current breakingHigh Electrical arc interrupting capacityapprox. 10 times that of air (depending on density) Heat transferTwice better heat transfer than airThese properties make it possible to significantly reduce the size of Electrical equipment and the operating energy of Circuit breakersWhy use SF6?Dielectric strength / SF6 Boiling point ( C)non-toxictoxicverytoxic?19832014 Source: ETH Z rich, Biasiutti& Zaengl, 1983 Search for Alternatives to SF6 Search for alternative gases started already in the 1980 sAlternatives to SF6 VacuumisanalternativeforMVapplications, ForHVapplicationsitwasnecessarytofindana lternativegasorgasmixture. CircuitbreakersdevelopedwithCO2(andO2) Capplications. GasmixturesincludingFluroketonearealsopr oposedbutlimitedtoaminimumtemperatureof5 C( ).More information to come inAlternatives to SF6SF6is main gas for high voltageinsulation and interruptionGrid Solutions cooperation with 3M19801997193820102014 First experiments on SF6as quenching mediumSF6is listed in the Kyoto protocol as a Greenhouse GasAlternative to SF6 g3fluorinated nitrile2,3,3,3-tetrafluoro-2-(trifluorom ethyl)

8 Propanenitrileheptafluoroisobutyronitril eCAS # 42532-60-5A gas mixture of 3 MTMN ovecTMcompound and CO2A new compound developed specifically for switchgear applicationsAlternative to SF6 g3 Ratio of Novec molecule in g3depends on vapor pressure at minimum operating temperature For -25 oC, a slight overpressure allows to reach the SF6dielectric strengthDielectric withstand is 85 to 100 % that of SF6 Alternative to SF6 g3 Dielectric strength increase when Novec is addedTemperatureriseTests on GIS itemsInterruptionTests on 145 kV LT CBCO2/ L-21609CO2/ L-21609 Voltage withstandTest duties performed on GIS & AIS productsSwitchingTests with GIS disconnectorsAlternative to SF6 g3380 kg eq. CO298 % lower GWP than SF6SF623,500 kg eq. CO2 Calculation method 100-yr ITH IPCC 2013 For 1 kg 4 % of 3M NovecDrastic reduction of global warming potentialAlternative to SF6 g3420 kV GIL:Pilot project in UKFirst pilot project with National Grid 300 m GIB at Sellindge substation, in Kent 420 kV, 63 kA, 4000 A Over both g3busducts: 11670 t eq.

9 CO2will be saved during the operation period SF6 (GWP 23500)g3(GWP 327) tons of tons of g3 Gas emissions during 40 years ( %/year)Gas emissions during 40 years in equivalent carbon11750 tons eq. CO274 tons eq. CO2 GIBA lternative to SF6 high - Voltage Circuit Phenomena in HV Circuit Extinction Related to high - Voltage Circuit 1 on TRVA nnex 2 on New Test Procedure T100aAnnex 3 on Transformer Limited FaultsCircuit breaker Rated Characteristics Rated maximum Voltage Rated insulation level* Rated frequency Rated continuous current Rated short-time and peak current Rated short- Circuit making and breaking current Rated operating snetwork.* In IEEE , but Rated dielectric withstand capabilities in IEEE Characteristics / Rated Maximum values have been generally harmonized between IEC and ANSI/IEEE-Medium voltage3,6 * * 12 15* * 24 * 27* 36 38* * 52 kV.*: values used in North America ( and 27 kV are preferred to 15 and kV) - high 100** 123 145 170 245 300** 362 420** 550 800 1100** 1200** kV.

10 **: values in IEC onlyIEEE values are given in of IEEE Characteristics / Insulation LevelThe insulation level/dielectric withstand capability is given by the withstand Voltage at power frequency(50 Hz or 60 Hz), the lightning impulsewithstand Voltage , the switching impulsewithstand Voltage (Ur 362 kV).These values characterize the dielectric stresses that the Circuit breaker must withstand with a very high probability of Characteristics / Insulation Level. Closing operation by Circuit - breaker (A) can produce an overvoltage(switching impulse) on Circuit - breaker (B) Origin of a switching impulseABVoltage at line end BRated Characteristics / Insulation Level. Lightning impulse Voltage Switching impulse s250 s50 s2500 sA lightning impulse Voltage rises faster than a switching impulse Rated Characteristics / Insulation LevelInsulation levels in IEEE for rated voltages 245 Characteristics / Insulation LevelInsulation levels in IEEE for rated voltages 245 kVNotes to Table 1 Rated Characteristics / Insulation LevelInsulation levels in IEEE for rated voltages 245 kVPower Frequency Tests for Ur= 245 kV Explanation for standard value of 460 kV specified for wet testSwitching surge of 3 on one terminal: 3 x 245 2 / 3 = 600 kVEquivalent power frequency value: 600 x / 2 = 318 kVPower frequency Voltage on opposite terminal: 245 / 3 = 141 kVPower frequency Voltage between terminals: 318 + 141 460 kVPower Frequency Tests for Ur= 145 kV Explanation for standard value of 275 kV specified for wet testSwitching surge of 3 on one terminal.