电气工程及自动化专业外文翻译--无人值班变电站与变电站自动化.doc

电气工程及自动化专业外文翻译--无人值班变电站与变电站自动化.doc

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Unattendedsubstationandsubstationautomation

Thedevelopmentofautomaticreclosingmadetheunattendedsubstationpractical.Automaticoperation,withoutthecontinuouspresenceofanattendant（operator）,wasfirsttriedonthesynchronousconvertersubstationssupplyinganinterurbanelectricrailwayin1914.Intheearly1920s,thedevelopmentofautomaticreclosing,protectiverelays,andmeansforautomaticcontrolofvoltagemadeitpossibleforacsubstationstobecompletelyautomatic.Duringtheperiodwhenthesubstationshadtobecontrolledmanually,itwasnecessarythattheyhandleenoughpowertojustifytheoperator`swages.Thisdictatedlargestations,frequentlyservinglargeareasbymeansofmanyfeeders.Thefeedersthatservedthemoredistantpartsofanareahadtogoalongwaybeforetheypickedupanyload.Furthermore,astheloadonalargesubstationgrows,transformercapacityhastobeadded.Thisincreasestheshort-circuitcurrentonthesecondarysidesometimestheshort-circuitcapacityexceedstheinterruptingcapacityofthecircuitbreakersalreadyinstalled.Appropriateremediesincludebussectionalizing,theinstallationofreactorsorsomecombinationofthetwo.Suchmeasuresarefrequentlyexpensiveandinconvenientandtheyconstituteanundesirablelimitationonoperatingflexibility.

Oncetheunattendedsubstationbecameareality,thesubstationcouldbemadesmaller.Locatednearertheload,andlongfeederswerenolongernecessary.Thisnewmethodofdistributionhadbecomeavailablesinceloadgrowthcouldnowbeaccommodatedbyinstallinganothersubstationthatcouldcarrypartsofthearealoadsformerlycarriedbyadjacentsubstations.Usually,thereisnointerconnectionbetweenthecircuitsenergizedbythevarioussubstations.Consequently,thereisnoincreaseinshort-circuitseverity.however,atthedistributionlevel,tieswitchesareusedtoswitchfeedersorfeedersectionsbetweentransformersinthesamestationortoadjacentsubstationsforsubstationtransformerloadmanagement.

Automaticcontrolhasbeenappliedtolargerandlargersubstations,andtomanyhydroelectricgeneratingstations.Itisalsousedonindividualcircuitsandequipmentinmanyattendedstations.Forexample,eveninmanystationswhereanoperatorisonduty,outgoingoverheadfeedersarecontrolledbyautomaticreclosingrelays.Undersomecircumstances,itmaybeimpracticaltomakeastationcompletelyautomatic.Thesecircumstancescouldexistbecauseoftechnical,economic,orsafetyconsiderations.Astationneednotbeattendedeventhoughitisnotfullyautomatic,itispossibletocontrolastationfromanotherlocation,suchasalargerattendedstationorthesystemoperatingoffice.Thiscanbedonebymeansofsupervisorycontrol（aformofremotecontrol）.

BymeansofaSCADAsystem,anoperatoratadispatchcentercancauseoperationssuchastheopeningandclosingofbreakers,thestartingandstoppingofcondensers,andthechangingofthetapsontransformerswithloadtapchanger.Theoperatorcanreceiveanindicationthattheoperationhasbeencompleted.Allofthiscanbedoneoveravoice-gradecommunicationchannel.Itistheuseofvoice-grade,two-waycommunicationchannelsthatdistinguishessupervisorycontrolfromdirect-wireremotecontrol;Thelatterrequiresonedirect-wirecircuitforeachcontrolfromdirect-wireremotecontrol;Thelatterrequiresonedirect-wirecircuitforeachcontrolleddevice.SCADAequipmentsupplementsautomaticcontrol.Alloftheprotectiverelaysandmostofthecontrolrelaysrequiredforautomaticcontrolarealsonecessarywhensupervisorycontrolisused.Onlytheinitiatingdevicesmaybedifferentoromitted.Forexampleafullyautomaticsynchronouscondenserisstartedandstoppedbyaninitiatingdeviceresponsivetovoltageorcurrentorboth.Inaddition,therearemanyprotectiveandcontrolrelays.Ifthecondenseristobecontrolledbysupervisorycontrol,alltheotherdevicesarestillnecessary,andonlytheinitiatingdevicescanbeomitted.

Withtherecentrevolutioninmicroelectronicperformanceandcosts,digitalautomationsystemsarenowbeingdevelopedforpowersystems.Theseautomationsystemsprovideanintegratedsystemsconceptforprotection,control,andmonitoringfunctions.Theapproachutilizesdistributedmicroprocessor-basedmoduleslocatedwithinthesubstationsandortonthetransmissionanddistributionsystem.Thisprovidesprotectionandcontroldecisionsoutonthesystemwherethedataislocated.Byautomatictransmissionanddistributionsystems,majorbenefitswillbeobtained.Thereincludegreaterutilizationofexistingfacilities,reductionofcommunicationrequirements,deferralofmajorsysteminvestments,optimizedoperationsandmaintenance,improvedsystemreliability,moreefficient-systemoperationthroughlowerlossesan