《电力系统继电保护及应用》课件-8. Voltage transformer and its configuration wiring

Voltagetransformeranditsconfigurationwiring1Theroleandcommontypesofvoltagetransformers2RatedvoltageonthesecondarysideofthevoltagetransformerCONTENTS3Configurationofthesubstationvoltagetransformer4WiringofthevoltagetransformerCONTENTSTheroleandcommontypesofvoltagetransformers01TheroleandcommontypesofvoltagetransformersThevoltagetransformerisusedtoisolatethesecondarycircuitfromthehighvoltageprimarycircuit,andaccuratelytransformtheprimaryhighvoltagetotheallowablevoltageofthesecondaryprotectionandthesecondaryinstrument,sothattherelayandinstrumentcanoperateatlowvoltageandaccuratelyreflecttheoperationofthehighvoltageequipmentinthepowersystem.Therearemanytypesofvoltagetransformers,includingelectromagneticvoltagetransformers,capacitancevoltageextractionvoltagetransformers,andelectronicvoltagetransformers.TheroleandcommontypesofvoltagetransformersTheadvantageoftheelectromagneticvoltagetransformerisitssimplestructureandgoodtransientcharacteristics.Itsdisadvantageisthatitiseasytoproduceferromagneticresonance,resultingintheovervoltageoftheprimarysystem,easysaturation,resultingininaccuratemeasurementandoverheatingdamage.Theadvantageofcapacitivevoltagetransformers(i.e.,capacitivevoltageextractionvoltagetransformers)isthatthereisnoferromagneticresonanceproblem.Itssteady-stateoperatingcharacteristicsarebasicallythesameastheelectromagneticvoltagetransformer,butitstransientcharacteristicsarepoor.Whenashort-circuitfaultoccursinthesystem,thetransientprocessdurationofthevoltagetransformerisrelativelylong,whichaffectstheworkingaccuracyoffastprotection.

Atpresent,capacitivevoltagetransformersarewidelyusedinpowersystems.TheroleandcommontypesofvoltagetransformersInsubstations,thevoltagetransformeronthebusisusuallyequippedwithoneormoremainsecondarywindings

connectedbystarandanauxiliarysecondarywindingconnectedbyopendelta.Accordingtothepurpose,themainsecondarywindingofthevoltagetransformercanalsobedividedintoprotectionvoltagetransformerandmeasurementvoltagetransformer,butinmanycases,theprotectionandmeasuringdeviceoftensharethesamemainsecondarywinding,obviously,thesecondarywindingshouldbeabletomeettherequirementsofboththeprotectionandmeasuringdevice;Theauxiliarysecondarywindingconnectedbyopendeltaisusedforprotectivedeviceandautomaticdevice.Theaccuracyleveloftheprotectivevoltagetransformeris3Pand6P,andthemeasuringvoltagetransformerhas5standardaccuracylevels,namely0.1,0.2,0.5,1and3.TheroleandcommontypesofvoltagetransformersRatedvoltageonthesecondarysideofthevoltagetransformer02Ratedvoltageonthesecondarysideofthevoltagetransformer

Configurationofthesubstationvoltagetransformer03Configurationofthesubstationvoltagetransformer1.InstallationpositionofthevoltagetransformerInsubstations,voltagetransformersaremainlyinstalledonbusbarsorlinesandtransformerbranches.Insubstationsof220kVandbelow,thevoltagesusedbytheprotection,measurementandmeteringdevicesofbranchcircuitssuchastransformersandlinesareusuallytakenfromthesecondarysideofthebusbarvoltagetransformer.ConfigurationofthesubstationvoltagetransformerWhenthereisapowersupplyontheoppositesideoftheline,inordertodetectthelinevoltagetorealizenovoltageclosing,avoltagetransformeroravoltageextractiondeviceshouldbeinstalledonthelinesideofthecircuitbreaker.Atthe220kV,110kVlargegroundcurrentsystem,thelinevoltagetransformerusuallyusesasinglephasevoltagetransformer,installedonphaseAatthelineoutletgantry.Inasmallgroundcurrentsystem,thelinevoltagetransformerisgenerallyavoltagetransformerconnectedbetweenthetwo-phasevoltages.Configurationofthesubstationvoltagetransformer2.GeneralconfigurationprincipleofthevoltagetransformerThenumberandaccuracylevelofsecondarywindingofbusvoltagetransformerin220kVsubstationshallmeettherequirementsofeachprotection,measurement,meteringandotherautomaticdevice.Whentheprotectionandmeasurementandmeteringdevicesshareasetofsecondarywindings,theaccuracylevelofthesecondarywindingshallbeselectedaccordingtothemeasurementandmeteringrequirements.Thebusbarvoltagetransformerwithvoltagelevelof220kVandbelowshouldbeequippedwithtwoorthreeorevenfoursecondarywindings,oneofwhichcanbeconnectedinanopentriangle,andtheotherwindingscanbeconnectedinastarshape.Sincethevoltagesofthetwosetsofprotectiondevicesinthedualconfigurationarerequiredtobeobtainedfromdifferentsecondarywindingsofthevoltagetransformer,the220kVvoltagetransformershouldbeequippedwith3secondarywindings,andifnecessary,anadditionalsecondarywindingformeteringcanbeadded.Wiringofthevoltagetransformer04WiringofthevoltagetransformerTakethe220kVTYDcapacitivevoltagetransformerasanexample,Sincethebusbarvoltagetransformersareindependentlyarrangedinthreephases,thethree-phasevoltagesareledfromtheTVseco