电气工程及自动化专业英语2020.1 IntroductionFig.20-1 Schematicofovercurrentprotection20.2 ProtectionofRadialSystems1)UndernormalloadconditionsthecircuitbreakersB0,B1andB2donotoperate.2)Underfaultconditionsonlytheclosestbreakertotheleftofthefaultshouldoperate;thisprotectsthesystembyclear...
20.1 IntroductionFig.20-1 Schematicofovercurrentprotection20.2 ProtectionofRadialSystems1)UndernormalloadconditionsthecircuitbreakersB0,B1andB2donotoperate.2)Underfaultconditionsonlytheclosestbreakertotheleftofthefaultshouldoperate;thisprotectsthesystembyclearing(andreenergizing)thefaultwhilemaintainingservicetoasmuchofthesystemaspossible.3)Intheeventthattheclosestbreakerfailstooperate,thenextbreakerclosertothepowersourceshouldoperate.Thisprovisioniscalledbackupprotection.Fig.20-2 Radialsystem20.3 SystemWithTwoSourcesFig.20-3 Systemwithtwosources20.4 Impedance(Distance)RelaysFig.20-4 Zoneofoperationofimpedancerelay20.4 Impedance(Distance)RelaysFig.20-5 Faultpointsandprotectedzones20.5 DifferentialProtectionofGeneratorsFig.20-6 Generatorprotectionbydifferentialrelaying20.5 DifferentialProtectionofGeneratorsFig.20-7 Proportionaldifferentialrelay20.5 DifferentialProtectionofGeneratorsFig.20-8 Operatingregionofdifferentialrelay20.6 DifferentialProtectionofTransformersFig.20-9 DifferentialprotectionofY-Ytransformerbank20.6 DifferentialProtectionofTransformersFig.20-10 DifferentialprotectionofD-Ytransformerbank20.7 ComputerRelaying1)Lowcost.2)Lowinventory.Afewstandardproductsmaybevariouslyandeasilyconfigured.3)Lowmaintenance.4)Veryflexibletrippingcharacteristicsthatcanbechangedwithsoftwareandformaremotelocation.5)Self-monitoringwiththeabilitytoreportrelayfailureautomatically.20.7 ComputerRelaying6)Asinglerelaywithasinglesetofinputscanbeprogrammedtocarryoutanumberoffunctions(e.g.,distanceprotectionformultiplezones).Insteadof,say,threeimpedancerelays,eachwithadifferentreach,tocoverthreedifferentzones,wecancombinethethreefunctionsintoasingleunit.7)Reducedpanelspaceandstationpower.20.7 ComputerRelaying8)Additionalfunctions.Inadditiontotheirprimaryfunctionofprovidingprotection,microprocessorrelaypackagescanalsoprovidecommunicationsandrecordkeeping.Voltageandcurrentreadingsandrelayandapparatusstatuscanbetransmittedtosystemoperators.Detailedfaultoperatingrecords(includingoscillographsoffaultcurrentsandvoltages)canbestoredanddisplayed.Linerelayscancalculateanddisplayfaultlocations.Linerelayscanhavearevenuemeteringcapability.20.7 ComputerRelaying1.tripping2.intact3.critical4.relay5.operating6.relay7.plunger8.solenoid9.latch10.in20.7 ComputerRelaying11.transverse12.backup13.protection14.pairwise15.dash16.damping17.braking18.opposing19.spiral20.tension20.7 ComputerRelaying21.directional22.impedance23.driving-point24.designation25.dot26.differential27.phase-phase28.restraining29.cancel30.autotransformer31.microprocessor-based32.recordkeeping
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