控制电缆烧损事故之分析改善与预防对策

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1、1Chapter4ModelingofNonlinearLoadOrganizedbyTaskForceonHarmonicsModeling&SimulationAdaptedandPresentedbyPauloFRibeiroAMSCMay28-29,2008Contributors:S.Tsai,Y.Liu,andG.W.Chang2ChapteroutlineIntroductionNonlinearmagneticcoresourcesArcfurnace3-phaselinecommutedconvertersStaticvarcompen

2、satorCycloconverter3IntroductionThepurposeofharmonicstudiesistoquantifythedistortioninvoltageand/orcurrentwaveformsatvariouslocationsinapowersystem.Oneimportantstepinharmonicstudiesistocharacterizeandtomodelharmonic-generatingsources.CausesofpowersystemharmonicsNonlinearvoltage-cu

3、rrentcharacteristicsNon-sinusoidalwindingdistributionPeriodicoraperiodicswitchingdevicesCombinationsofabove4Introduction(cont.)Inthefollowing,wewillpresenttheharmonicsforeachdevicesinthefollowingsequence:HarmoniccharacteristicsHarmonicmodelsandassumptionsDiscussionofeachmodel5Chap

4、teroutlineIntroductionNonlinearmagneticcoresourcesArcfurnace3-phaselinecommutedconvertersStaticvarcompensatorCycloconverter6NonlinearMagneticCoreSourcesHarmonicscharacteristicsHarmonicsmodelfortransformersHarmonicsmodelforrotatingmachines7Harmonicscharacteristicsofiron-corereactor

5、sandtransformersCausesofharmonicsgenerationSaturationeffectsOver-excitationtemporaryover-voltagecausedbyreactivepowerunbalanceunbalancedtransformerloadasymmetricsaturationcausedbylowfrequencymagnetizingcurrenttransformerenergizationSymmetriccoresaturationgeneratesoddharmonicsAsymm

6、etriccoresaturationgeneratesbothoddandevenharmonicsTheoverallamountofharmonicsgenerateddependsonthesaturationlevelofthemagneticcorethestructureandconfigurationofthetransformer8HarmonicmodelsfortransformersHarmonicmodelsforatransformer:equivalentcircuitmodeldifferentialequationmode

7、lduality-basedmodelGIC(geomagneticallyinducedcurrents)saturationmodel9Equivalentcircuitmodel(transformer)Intimedomain,asinglephasetransformercanberepresentedbyanequivalentcircuitreferringallimpedancestoonesideofthetransformerThecoresaturationismodeledusingapiecewiselinearapproxima

8、tionofsaturationThismodelisincrea