The Configuration and Communication of Integrated Substation Automation Systems 配置及变电站综合自动.docx
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TheConfigurationandCommunicationofIntegratedSubstationAutomationSystems配置及变电站综合自动
TheConfigurationandCommunicationofIntegratedSubstationAutomationSystems
Abstract
Basedonadiscussionofthefeatureofasubstation,thepaperpresentstheconceptthatasubstationiscomposedofbasicunits(BC).ThehardwarestructureoftheIEDofaBCisdescribed.Next,thepaperdiscussesthecommunicationmodeofthecurrentintegratedSubstationAutomationSystems(ISA)anddescribesthehardwarestructureandthefunctionsoftheISAwithfieldbus.AtlastthepaperpresentstrendsinthedevelopmentofISA.
Keywordssubstationautomationcommunicationfieldbus
1.Introduction
Sincethebeginningof90`s,hundredsofISAsystemhavebeenputintooperationinChina.Thesesystemshaveplayedaveryimportantroleinsubstationperformancehavebeendemonstratedinmanyways.Thissystemshouldbeamulti-functionintegratedanduniformlydesignedrealtimecontrolsystemwithhighefficiencyandreliability.Itshouldimplementamostallthefunctionsofsecondaryequipmentofmodernsubstation,realizetherealtimedatasharingandexchange,andshouldbeexpandableforfutureuse.HowtodesignanISAsystemtomeetalltheaboverequirementsisdiscussedinthepaper.
First,afteradiscussionofthefeatureofsubstation,thepaperpresentstheconceptthatasubstationiscomposedofbasicunits(BC),suchaslines,transformers,bussesandVoltAmpereReaction(VAR)compensationequipment,andsoon.ThecircuitbreakersandswitchesaremergedintherelevantBCsastheirattachedcontrolfacilities.ThehardwarestructureofaBCisdescribed.Next,thepaperdiscussesthecommunicationmodeofthecurrentISAandpointsoutthefieldbuswouldbethewaytorealizereliable,real-timeandaccurateinformationcommunicationamongintelligentelectronicdevice(IED).Then,ifpresentstheconfigurationandfunctionsofthedistributedISAwithfieldbus.Atlast,thepaperpresentstrendsinthedevelopmentofISA.
2.BasicUnitsandConstruction
Asubstationisaveryimportantunitinpowersystemforpowertransmissionanddistribution.Asubstationisrequiredtoruncontinuously,reliablyandstably.Substationsofvariousvoltagelevelsandcapacityhaveasimilarconfigurationwhichiscomposedofpowertransmissionanddistributionfacilitiessuchastransformers,VARdeviceswithdifferentvoltagelevels.Thedistinctionbetweendifferentsubstainsisthequantityandvoltageleveloffacilitiesandthewayconnectiononly.
Tomonitorandcontrolthesubstationoperation,abusisequippedwithpotentialtransformers(PT)andtherearecurrenttransformers(CT)ineachwindingofthetransformer,eachlineandtheswitchgearbayoftheVAPequipment.INthesecondarysystem,instantaneousvaluesofvoltageandcurrentareobtainedthroughPTandCT,andthesevaluesarefurtheranalyzedandprocessedtogiveoperationaldataofthesubstationsuchasvoltage,currentandpoweretc.Nom-electricaldatasuchasoiltemperatureandgassignalsarealsoprovidefortransformersandVARequipment.Statusdataofcircuitbreakers,isolatorswitchesandotherauxiliaryequipmentintheswitchgearbaysaregatheredthroughauxiliarycontactsandtransducers.Thesubstationsecondarysystemcollectsandprocessesallthesedatatodetectanyfaultorabnormality.Ifthereisafault,thesecondarysystemwillsendoutacircuitbreakertrippingcommandtotheswitchbaycorrespondingtothefaultedequipmentsothatthefaultcanbeisolated.Ifthereisabnormality,awarningsignalwillbegiven.
Ithasbeenshownbyrelevantreferencethatthefaultcharacteristicsofbuses,lines,transformersandVARequipmentaredifferentfromeachotherasaresultoftheirdifferentphysicalfeature.Thereforerequirementsfortheirmonitoringandcontrolaredifferentfromeachother.
Forfaultsinlines,transformers,VARequipmentorbuses,therearenoothercontrolmeasuresthantrippingthecircuitbreakersofthecorrespondingequipment.
Undernormaloperationcondition,transformersandVARequipmentparticipateinvoltageandVARcontrolcoordinatedbythesystemtomeettherequirementsofpowernetworkvoltagelevelandVARcompensation.
Coordinatedbythesecondarysystem,severalcircuitbreakersmaybecontrolledtomaintainpowersystemstabilityorpowersupplyreliabilityofthesubstation.Commonexamplesareunderfrequencyloadsheddingandbusautomatictransfer.
Tosummarize,themainfeaturesofasubstainsystemare:
Buses,lines,transformersandVARdevicesarethebasicequipmentinasubstation.Theyfunctiontogethertotransferanddistributepower.
Requirementsforthemonitoringandcontrolofbuses,lines,transformersandVARdevicesdifferfromeachother.
Alargeamountofdatainasubstationisfromswitchgearbays,asmalldatatothem.
Protectionandmeasurementformonitoringhavethesamedatasourcebutdifferentrequirementsforsamplingfrequencyandcontrolalgorithms.
Relayprotectionisafundamentalfunctionanditsnormaloperationshouldbeensuredevenifotherdevicesfailtowork.
Thereislittleinformationexchangebetweenswitchgearbays.
Thecontrolofacircuitbreakerinswitchgearbaysmayhavevariouscausesuchaslinefaults,lossofsystemsynchronism,equipmentoverloading,underfrequencyloadshedding,normalnetworkoperationsandsoon.Whateverthecauseis,theoperationisthecontrolofcircuitbreakers.
TransformersandVARdeviceshavetwokindsofcontrol,i.e.,controlinfaultcondictionsandinnormalsystemoperations.
Basedontheaboveanalysisandfromthepointofviewofmonitoringcontrolandmanagementofpowertransferanddistributioninsubstation,thispaperproposesthatasubstationconsistsofsuchBCsasbuses,lines,transformers,VARequipmentandsoon.ABCprovidesdatathroughoneorseveralswitchgearbaystoandreceivescontrolcommandsfromthesecondarysystem.EachBChasitsowncharacteristicsandrequirementsformonitoringandcontrol.
ThusaBCinsubstationcanbetreatedasabasicresearchobjectofmonitoringandcontrol.Thesetofallbasicresearchobjects,managed,coordinatedandcontrolledbythesubstationmaincomputer,formaanISAsystem.
ThehardwarestructureofaBCisnotedasIED.AccordingtothefunctionalrequirementsofaBC,IEDisdesignedbythefaultindependentruleandfunctionindependentrule.EachBChasitscorrespondingIEDwhichmainlydiffersinI/OinterfacesfromthatofanotherBC.Forexample,thetransformerIEDnotonlyinterfaceswithtemperatureandpressuretransducers,butalsohasalargernumberofI/OthanalineIEDhas,Itmustcontrolallthebreakersonthesideofeachwindingunderfaultconditionsandcontroltheon-loadtap-changerundernormaloperations.TheIEDofaVARdeviceoralineBCprovidesaserialporttocommunicatewithaintelligentVARdevice,ortheprotectiondevicelocatedontheothersideofaline.AtypicalIEDhardwarestructureofaBCisshowninFig,.1.
TheAC/DCsamplingandBinaryI/OpartsareconnectedtoabaythroughPT/CTandopticalinsulators,acquiringdatafromthebayandcontrollingthebreaker.TheProcessControlpartanalyzes,calculatesandprocessestheacquireddata,andperformsprotectionfunctionsbytrippingthebreakeriffaultsaredetected.ThroughFieldbusinterface,anIEDcommunicateswiththesubstationcomputersystem(SCS)orotherIED.IttransmitsrealtimedatatotheSCSforsupervisionandreceivescommandsfromSCSorotherIEDforcontrol.
MMIisusedfordisplayingtheacquireddataandparameters,testingandmaintenanceoftheIED.
ThebusIEDacquiresdirectlythecurrentandstatusdatafromthebaysanddetectsbusfaults.Ifafaultisdetected,allbreakersofallunitsconnectingthebusaretrippedbythebusIED.
ThefunctionofunderfrequencyloadsheddingisrealizedbythebusandlineIED,coordinatedbytheSCS.
3.InformationExchangeandFieldBus
ThecommunicationinterfacebetweenthecurrentIEDofISAismainlybyRS-422/485seriesportandonlyafewisbylocalareanetwork(LAN).UsingRS-422/485communicationinterface,thelinkamongnodescanbedone,butthenumberofnodeslinkedcannotbemorethan32andcannotsuitthefuturedemandsofISA.Inaddition,thecommunicationmodeismaster/slaveandhasdrawbackasfollows:
Onlyonenodeismaster,andtheothersareslavesinthecommunicationnet.Ifthemasternodeisatfault,thesystemwillimmediatelyfail.
Thecommunicationmodeofmaster/slavestructureisunbalanced.Theslaverespondstothecommandsfromthemasterandsendsdatatothemaster.Theefficiencyofdatatransmissionislowandimportantdataintheslavecannotbetransmittedimmediatelyuntilitreceivesthecommandfromthemaster.Thelargerthesystemscale,thelowerthereal-timeofsystemperformance.
Themaster/slavecommunicationmodecannotmeettherequirementsofcommunicationbetweenanytwonodes.
UsingRS-422/485seriesportinterface,itiseasytoconnecteachother.ButtheprotocolamongtheIEDisdifferentandnostandardinchinaisfollowed.Therefore,thecommunicationcontroliscomplicatedanditisdifficulttorealizehigh-speed,reliableandaccurateinformationexchangebetweenIED.Themediaforcommunicationislimitedandsystemsengineersareoccupiedwithprogrammingandtestingcommunicationsoftware.ApplyingLANtechnology,thedatacanbetransmittedinhighspeedandthefunctionsofcentralprocessing.Butinthefieldofprocesscontrol,theadvantagesofLANarelessobviousowingtothefollowingreasons:
·IntheLAN,largequantityofdataaretransmittedinapackageofmessage,buttheyarenotfrequentlytransmitasmall