外文翻译原文-并联电容器开关的真空断路器电气寿命

VacuumCircuitBreakersElectricalLifeforShuntCapacitorSwitchingS.Griot1andA.Moreau11SchneiderElectric,ZACchampsaintange38760Varces,FranceAbstract-Inordertoimprovetheefficiencyofpowerdistributionandforeconomicreasons,thepowerfactoriscorrectedonmediumvoltageelectricalnetwork.Todothis,itismandatorytoswitchonceortwiceadayacapacitorbank.Vacuumcircuitbreakersarefrequentlyusedtoswitchcapacitorbanks.Anautomatedsystemisusedtoevaluatetheelectricallifeofvacuumcircuitbreakersdependingontheshuntcapacitorswitchingparameters.Testsconsistofopeningandclosingoperationsonathree-phasecircuitbreaker.Thissystemhastwomainadvantages;themaximumreactivepoweravailableis20Mvarat24kVwithinrushcurrentsupto22kA(commonvaluesincustomerapplicationsareunder10kA)andtheshortendurancetestdurationisonly8daysfor10,000operationscomparedto5weeksinlaboratories.I.INTRODUCTIONInpowerdistribution,capacitorbanksarewidelyusedtocorrectthepowerfactoronmediumvoltageelectricalnetwork.Thiscorrectionimprovestheefficiencyofelectricaldistributionandiscostsaving.Concerningthevacuumcircuitbreakersperformancesonshuntcapacitorswitching,thefocusisgenerallyonstandardrequirements,1,2.Capacitorbanksareswitchedusuallyonceortwiceperday,asdescribedin3.Thus,avacuumcircuitbreaker,withanelectricallifeof10,000operations,couldoperateforbetween14and33years.TableIcomparestherequirementsoftheIECandIEEEStandards,1,2,andthecustomersneeds.TABLE1.COMPARISONBETWEENTHESTANDARDSANDTHECUSTOMERSNEEDSMoststudieslike5describetheperformanceofvacuumcircuitbreakersinthelimitednumberofoperationsprescribedin1,2.Reference4describesthebehaviourofthevacuumcircuitbreakersupto1,000operations.Thereforeuntilnow,themanufacturerrequiresthefeedbackfromtheend-userstoevaluatetheperformanceoftheirequipment.Thispaperdescribesanautomatedsystemthatpermitsthestudy,atafastpace,theperformanceofvacuumcircuitbreakerslifecycle.Hencetheinfluenceofawiderangeofshuntcapacitorswitchingparameterscanbeinvestigatedindependently.II.CHARACTERISTICSOFSHUNTCAPACITORSWITCHINGTheswitchoftheshuntcapacitorisparticularcomparedtotheswitchofaresistiveorinductiveload.Duringshuntcapacitorswitching,themostimportantphenomenaappearduringtheclosingandtheopeningoperations.Duringtheclosingoperation(representedbythen1ontheFig.1),theinrushcurrenthasastrongimpactonthevacuuminterrupterselectricallife.Duringtheopeningoperation(representedbythen2ontheFig.1),thecurrenttointerruptislow(incomparisonwiththeshortcircuitcurrent)becauseitistheratedcurrentofthecapacitorbank.But,hreephasesnetworkswithungroundedneutralofthecapacitorbank.Withouttheimpactoftheinrushcurrent,theenduranceoftheopeningoperationisnotreallyaproblemforthevacuuminterrupter,asshownin3.Fig.1.TypicaloscillogramofshuntcapacitorswitchingAtthestartoftheclosingoperation,thecircuitbreakerreceivesanordertoclose.Themobilecontactsofthecircuitbreakeraremovedbythemechanism.Theelectricfieldincreasesasthegapbetweenthecontactsreduces.Anarcoccurswhentheelectricfieldissuperiortothedielectricstrengthoftheshortgapbetweenthecontacts.Thisisthestartofthepre-strikingtime.ThisarccontinuesuntilthecontactsareXXIVthInt.Symp.onDischargesandElectricalInsulationinVacuum-Braunschweig-2010978-1-4244-8365-5/10/$26.002010IEEEcompletelyclosed.Thisistheendofthepre-strikingtime.Astheinrushcurrentoftheshuntcapacitorhasahighfrequencyandanimportantpeakvalue,theenergytransferredfromthearctothecontactduringthepre-strikingtimeisimportant.Thisenergyinducessmallweldingpointsonthesurfaceofthecontact.Duringtheopeningoperation,theratedcurrent(generallybetween100and1,000A)tobreakismuchlowerthanashortcircuitcurrentortheinrushcurrent.Thearcbornwiththeseparationofthecontactshasalowenergyandcannotreshapebyerosionthedamagecausedbytheinrushcurrentonthesurfaceofthecontact.TherecoveryvoltageisslowerthantheTransientRecoveryVoltageafterashortcircuitbreakbutreachesahighervalue.Thedielectricstrengthofthevacuuminterruptermustremainhighinspiteofthedegradationofthecontactssurfaceduetotheinrushcurrent.Takingintoaccountthewearduetotheinrushcurrentandtheerosionofthecontacts,theenduranceofthecircuitbreakermustbeevaluatedwithrespecttotheinstallationparameters.Itisimpossibletodissociatethevacuuminterrupterandthemechanism.Thesamevacuuminterrupterwillhavedifferentelectricallifedependingonthemechanismandthearchitectureofcircuitbreakers.Theenergyinsidethemechanismimpactsthespeedandtheeffortappliedtothecontacts.Thearchitectureimpactsthebouncingtimeduringtheclosingandopeningoperations.III.DESCRIPTIONOFTHEAUTOMATEDSYSTEMDuetothedifficultiestodothesetestswithadirectconnectiontothemediumvoltagenetwork,theprincipleofasyntheticlaboratoryisused,generally,forshortcircuitbreakingoperationtest.Theglobaldiagramofthetestingcircuitisrepresentedinfig.2.Theclosingandopeningoperationshavebeendissociated;ofcourse,bothoperationsmustbeexecutedtoobtaintherealperformanceofthecircuitbreaker.Thustheglobaldiagramissplitintwoparts.Thelefthandpartofthecircuitisusedtoreproducetheclosingoperation.Therighthandpartofthecircuitisusedtoreproducetheopeningoperation.Awiderangeofshuntcapacitorswitchingparameterscanbeobtainedby15differentcouplingsofcapacitorsand34differentcouplingsofinductances.Withtheautomatedsystem,upto510couplingsofthecapacitorsandinductancescanberealizedtoadjustthefrequencyandthemagnitudeoftheinrushcurrent.Often,thevaluesofinrushcurrentareupto10kApeak,whereashere,thegeneratedinrushcurrentisupto22kApeak.Thereactivepowersimulatedduringtheopeningoperationisupto10Mvarat12kVandupto20Mvarat24kV.Theautomatedsystemisdesignedtoreproducetheconditionsofanelectricalnetworkwithratedvoltageupto24kV.Fig.2.GlobaldiagramofthetestingcircuitTosimplifythediagram,theelementswhichguaranteethesafetyofpeoplearenotrepresented.Forfurtherdetails,ontheleftpart,theautomatedsystemgeneratestheinrushcurrentinordertoreproducetheclosingoperation(representedonFig.3).Ontherightpart,theautomatedsystemgeneratesahalfperiodofratedcurrentjustbeforetheapplicationoftherecoveryvoltageinordertoreproducetheopeningoperation(representedonFig.4).A.CircuitforclosingoperationsFig.3representsthelefthandpartoftheglobaldiagramusedtogeneratetheinrushcurrent.Fig.3.Diagramoftheinrushcurrentgeneration(themeaningofthenumbers,e.g.n14,canbefoundinthemaintext)Contactorsn4andn5areclosedduringtheclosingcycle.Alltheothercontactors(n6,n7andn8)areopen.Atthebeginning,thecircuitbreakerundertest(n1)isopen.Thecapacitors(n9)arechargedwiththethreechargers(n14).Thecircuitofthecapacitorchargersistypicallyusedinsyntheticlaboratory.Themainadvantageistobeabletohavetheconstantcurrentsupplythatprovidesaconstantchargeofthecapacitors.Eachphasecanbeprogrammedwithindependentanddifferentvaluesofvoltage,polarity,couplingsofcapacitorsandcouplingsofinductances.Afterthechargingofthecapacitors,theclosingoperationcanstartbyaclosingordersenttothecircuitbreakerundertest.Thethreecurrentscirculatefromthecapacitorsthroughtheinductances(n10)andthecircuitbreakeruntiltheearth.Thebehaviourofthecircuitbreakerismeasuredbysixvoltagesensors(n16and17),threecurrentsensors(n18)andthreedisplacementsensorsplacedinsidethecircuitbreakertomeasuretheinstantaneousmovementofthemobilecontactofthevacuuminterrupter.Thisisthecompletesequenceoftheclosingoperation.B.CircuitforopeningoperationsFig.4representstherighthandpartoftheglobaldiagramusedtogeneratetheratedcurrentandtherecoveryvoltage.Fig.4.DiagramofthecurrentandtherecoveryvoltagegenerationThecontactor(n5,Fig.3)isopenandthecontactors(n6andn4)areclosed.Atthebeginning,thecircuitbreakerundertest(n1)isclosed.Thelowvoltagecapacitors(n11)arechargedbythethreechargers(n15).Asalreadyexplained,eachphasecanbeprogrammedwithindependentanddifferentvaluesofvoltage,polarity,couplingsofcapacitorsandcouplingsofinductances.Afterthechargingofthecapacitors,theopeningoperationisstartedbyaclosingordersenttothecontactor(n7).Thethreecurrentscirculatefromthecapacitorsthroughtheinductances(n12)andthecircuitbreakeruntiltheearth.Duringthehalfperiodofthecurrent,thecircuitbreakerundertestisopenedaswellasthecontactorsn4andn6.Attheendofthecurrent,therecoveryvoltageisappliedtothecircuitbreakerforaprogrammeddurationbytheclosingofthecontactorn8.Therecoveryvoltageiscommontoallthreephases.IfthereisapresenceofaNonSustainedDisruptiveDischargeononeormorephases,thecomponents(n2andn3)allowthesystemtoidentifythedefaultphase.Thisisthecompletesequenceoftheopeningoperation.C.AutomaticfunctionsBothsequencesareautomatedbyaprogrammablecontroller.Betweeneachoperation,thecontrolleranalyzestherespondtimeofeachcriticalcomponentinordertocorrectandtomodifythenexttestsequence.Acomputerstoresallthedatameasuredbythesensors.Betweeneachtest,thecomputeranalysesandcalculatesallimportantvaluestogivetheauthorizationtotheautomationtocontinuethetests.Foreachclosingoperation,thecalculatedvaluesarethepeakvaluesoftheinrushcurrents,theirfrequencies,thechargingvoltagesofthecapacitorsandthepre-strikingtimesofeachphase.Foreachopeningoperation,thecalculatedvaluesarethermsvaluesofthebreakingcurrents,therecoveryvoltage,thenumbersandallthetimingsofthepossibleNSSDoneachphase.Foracompletesequence(aclosingoperationfollowedbyanopeningoperation),thedurationisaround70secondsdependingontheparameters.Animportantfeatureofthissystemisthat10,000operationscanbecompletedinonly8days.D.OscillogramsWiththisautomatedsystem,thefollowingtypicaloscillogramsarerecorded.Fig.5isatypicaloscillogramoftheclosingoperation.Ontheupperpart(n1)ofFig.5,theoscillogramrepresentstheinrushcurrentcorrespondingtotheshuntcapacitorswitchingparameterstobetested.Then3indicatesthestartingpointoftheinrushcurrent.Onthelowerpart(n2)ofFig.5,theoscillogramrepresentsthemovementofthemobilecontact.Then4indicatesthetimewhenthemobileandthefixedcontactsarecompletelyclosed.Thepre-strikingtimeistheintervalbetweenn3andn4.Fig.5.Typicaloscillogramoftheclosingoperation(themeaningofthenumbers,e.g.n1,canbefoundinthemaintext)Fig.6isatypicaloscillogramoftheopeningoperation.Ontheupperpart(n1)ofFig.6,theoscillogramrepresentsthehalfwaveofratedcurrentcorrespondingtotheshuntcapacitorswitchingparameterstobetested.Thecircuitgeneratesthehalfperiodofthecurrentthatthecircuitbreakermustbreak.Onthelowerpart(n2)ofFig.6,theoscillogramrepresentstherecoveryvoltage.ThevacuumcircuitbreakermustwithstandtherecoveryvoltagewithoutanyNSSDorrestrike.Fig.6.TypicaloscillogramoftheclosingoperationIV.RESULTSANDDISCUSSIONSBykeepingthesamearchitecture,mechanismandvacuuminterrupters,sometestsarerealizedwithdifferentshuntcapacitorswitchingparameters.AsummarycurveisshownintheFig.7andexplainsthenumberofoperationsbeforefailuredependingontheenergyoftheinrushcurrent.Thefailuremodesofthecircuitbreakercouldbeaweldingbetweenthemobilecontactandthefixedcontact(problemtoopenthecircuitbreaker)oratoolargedeformationofthecontact(problemtoclosethecircuitbreaker).Abrutalreductioninthelifetimeofthecircuitbreakerisfoundforenergyofinrushcurrentexceedingacriticalvalue.Asimilarbehaviourhasbeendescribedby6relatingtheeffectofenergyofinrushcurrenttotheNSSDoccurence.Fig.7.NumberofoperationsbeforefailureagainsttheenergyoftheinrushcurrentWiththecalculationoftheautomatedsystem,theFig.8representsthepre-strikingtimeofeachphaseagainstthenumberofoperations.Onecanseethestablebehaviourofthepre-strikingtimewiththenumberofoperations.Fig.8.Pre-strikingtimeagainstthenumberofoperationsV.CONCLUSIONInthispaper,asynthetictestlaboratoryispresentedtotesttheelectricalenduranceofthree-phaseshuntcapacitorswitches.Testconsistsofclosingandopeningoperationsonathree-phasevacuumcircuitbreaker.Themaximumreactivepowertobetestedis20Mvarat24kVwithinrushcurrentsupto22kA.Oneadvantageofthisautomatedsystemistobeabletoexploremoreseverecasesthanthemajorityofcustomerapplications(under10kA).Theotheradvantageistheshortendurancetestduration:only8daysfor10,000operationscomparedto5weeksinlaboratories.Testsareunderwaytoexploreandtoevaluateeachfactorwhichimpactsthevacuumcircuitbreakerselectricallifeforshuntcapacitorswitching.Afuturepaperwillexposetheresul