1.Converter_Transformer

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1、ConverterTransformerHVDCSystemsfor…•EnergyTransmissionoverlongdistances•AsynchronouscouplingbetweenACRegionalnetworksPowerElectroniccircuitsareusedtoconvertACtoDC(Rectifiercircuits)orconvertDCtoAC(InverterCircuits).Bothofthesecircuitsarealsocalledconvertercircuits.Atransformerthat

2、hasoneofitswindingsconnectedtooneofthesecircuits,asadedicatedtransformer,isaConverterTransformerConverterTransformerinHVDCsystem….•SupplyofACvoltagesintotwoseparatecircuitsfeedingtherectifierbridgeswithaphaseshiftof30electricaldegreesforreductionofloworderharmonicsesp.5th&7thharmo

3、nics.•AsagalvanicbarrierbetweenACandDCsystemstopreventDCpotentialenteringintotheACsystem•ReactiveImpedanceintheACsupplytoreduceshortcircuitcurrentsandtocontroltherateofriseinvalvecurrentduringcommutation.ConverterTransformersfor12pulserectification….Primary:Star400kVACSecondary:Tw

4、owindingsconnectedtoconverter(Thyristors)connectedinseriestobuilduprequiredlevelofDCvoltageChoiceoftransformerdesignismainlyruledby….–transportrestrictions(dimensionsandweight)–numberofnecessarysparetransformers–technicalpossiblesolutionsforcoreandwindingsConverterTransformersfor1

5、2pulserectificationTypeofConnectionsNo.ofdesignXNo.Sparesofunitsrequired3PhaseStar-Delta&Star-2X22StarSinglephase2winding2X62Singephase3winding2x31Extendeddelta-2X21connection3Phase3winding2X21ConverterTransformer....DesignactivepartValveWinding(Y)TapWindingValveWinding(D)LineWind

6、ingHV-TerminalNeutral-TerminalSimplifiedconnectionoflinewindingsandtapwindingsWindingandcorearrangementConverterXmer&NormalACXmer…..•PolarityReversal•VoltageDistributioninOilBarrierSystem•Impedancevariationinfluence•OnloadTapChanger•HarmonicCurrents•Losses•DCMagnetisation•ShortCir

7、cuitForces•DCBushingsUnderPolarityReversal…..•Beginningvoltagestressdistributionscapacitive–OilisstressedmorethanPB•SuccessivelychangeovertoResistivedistribution–PBisstressedmore(almostallstressacrosssolidinsulation)•PDstressesunderDC–Sporadicpulsesatrandomintervals-Dischargesinoi

8、lgapsunderrapidchangesinvoltage-D