电气类英文翻译-电力系统的演化

EVOLUTIONOFELECTRICPOWERSYSTEMSThecommercialuseofelectricitybeganinthelate1870swhenarclampswereusedforlighthouseilluminationandstreetlighting.Thefirstcompleteelectricpowersystem(comprisingagenerator,cable,fuse,meter,andloads)wasbuiltbyThomasEdison-thehistoricPearlStreetStationinNewYorkCitywhichbeganoperationinSeptember1882.Thiswasadcsystemconsistingofasteam-engine-drivendcgeneratorsupplyingpowerto59customerswithinanarearoughly1.5kminradios.Theload,whichconsistedentirelyofincandescentlamps,wassuppliedat110Vthroughanundergroundcablesystem.Withinafewyearssimilarsystemswereinoperationinmostlargecitiesthroughouttheworld.WiththedevelopmentofmotorsbyFrankSpraguein1884,motorloadswereaddedtosuchsystems.Thiswasthebeginningofwhatwoulddevelopintooneofthelargestindustriesintheworld.Inspiteoftheinitialwidespreaduseofdcsystems,theywerealmostcompletelysupersededbyacsystems.By1886,thelimitationsofdcsystemswerebecomingincreasinglyapparent.Theycoulddeliverpoweronlyashortdistancefromthegenerators.Tokeeptransmissionpowerlosers(RI2)andvoltagedropstoacceptablelevels,voltagelevelshadtobehighforlong-distancepowertransmission.Suchhighvoltageswerenotacceptableforgenerationandconsumptionofpower;therefore,aconvenientmeansforvoltagetransformationbecameanecessity.ThedevelopmentofthetransformationandactransmissionbyL.GaulardandJ.D.GibbsofParis,France,ledtoacelectricpowersystems.GeorgeWestinghousesecuredrightstothesedevelopmentsintheUnitedStates.In1886,WilliamStanley,anassociateofWestinghouse,developedandtestedacommerciallypracticaltransformerandacdistributionsystemfor150lampsatGreatBarrington,Massachusetts.In1889,thefirstactransmissionlineinNorthAmericawasputintooperationinOregonbetweenWillametteFallsandPortland.Itwasasingle-phaselinetransmittingpowerat4,000Voveradistanceof21km.WiththedevelopmentofpolyphasesystemsbyNikolasTesla,theacsystembecameevenmoreattractive.By1888,Teslaheldseveralpatentsonacmotors,generators,transformers,andtransmissionsystems.Westinghouseboughtthepatentstotheseearlyinventions,andtheyformedthebasisofthepresent-dayacsystems.Inthe1890s,therewasconsiderablecontroversyoverwhethertheelectricutilityindustryshouldbestandardizedondcorac.TherewerepassionateargumentsbetweenEdison,whoadvocateddc,andWestinghouse,whofavoredac.Bytheturnofthecentury,theacsystemhadwonoutoverthedcsystemforthefollowingreasons;Voltagelevelscanbeeasilytransformedinacsystems,thusprovidingtheflexibilityforuseofdifferentvoltagesforgeneration,transmission,andconsumption.ACgeneratorsaremuchsimplerthandcgenerators.ACmotorsaremuchsimplerandcheaperthandcmotors.Thefirstthree-phaselineinNorthAmericawentintooperationin1893-a2,300V,12kmlineinsouthernCalifornia.Aroundthistime,acwaschosenatNiagaraFallsbecausedcwasnotpracticalfortransmittingpowertoBuffalo,about30kmaway.Thisdecisionendedtheacversusdccontroversyandestablishedvictoryfortheacsystem.Intheearlyperiodofacpowertransmission,frequencywasnotstandardized.Manydifferentfrequencieswereinuse:25,50,60,125,and133Hz.Thisposedaproblemforinterconnection.Eventually60HzwasadoptedasstandardinNorthAmerica,althoughmanyothercountriesuse50Hz.Theincreasingneedfortransmittinglargeramountsofpoweroverlongerdistancescreatedanincentivetouseprogressivelyhighervoltagelevels.Theearlyacsystemsused12,44,and60kV(RMSline-to-line).Thisroseto165kVin1922,220kVin1923,287kVin1935,330kVin1953,and765kVwasintroducedintheUnitedStatesin1969.Toavoidtheproliferationofanunlimitednumberofvoltages,theindustryhasstandardizedvoltagelevels.Thestandardsare115,138,161,and230kVforthehighvoltage(HV)class,and345,500and765kVfortheextra-highvoltage(EHV)class.Withthedevelopmentofmercuryarcvalvesintheearly1950s,highvoltagedc(HVDC)transmissionsystemsbecameeconomicalinspecialsituations.TheHVDCtransmissionisattractivefortransmissionoflargeblocksofpoweroverlongdistances.Thecross-overpointbeyondwhichdctransmissionmaybecomeacompetitivetoactransmissionisaround500kVforaround500kmforoverheadlinesand50kmforundergroundorsubmarinecables.HDVCtransmissionalsoprovidesanasynchronouslinkbetweensystemswhereacinterconnectionwouldbeimpracticalbecauseofsystemstabilityconsiderationsorbecausenominalfrequenciesofthesystemsaredifferent.ThefirstmoderncommercialapplicationofHVDCtransmissionoccurredin1954whentheSwedishmainlandandtheislandofGotlandwereinterconnectedbya96kmsubmarinecable.Withtheadventofthyristorvalveconverters,HVDCtransmissionbecameevenmoreattractive.ThefirstapplicationofanHVDCsystemusingthyristorvalueswasatEelRiverin1972-aback-to-backschemeprovidinganasynchronoustiebetweenthepowersystemsofQuebecandNewBrunswick.Withthecostandsizeofconversionequipmentdecreasinganditsreliabilityincreasing,therehasbeenasteadyincreaseintheuseofHVDCtransmission.Interconnectionofneighboringutilitiesusuallyleadstoimprovedsecurityresultsfromthemutualemergencyassistancethattheutilitiescanprovide.Improvedeconomyresultsfromtheneedforlessgeneratingreservecapacityineachsystem.Inaddition,theinterconnectionpermitstheutilitiestomakeeconomytransfersandthustakeadvantageofthemosteconomicalsourcesofpower.Theseben