电气工程专业英语section-6-1.ppt

Chapter6ElectricPowerSystems

Section1IntroductionTextNewWordsandExpressionsExercisesEndTranslationofNegativeSentences

Section1IntroductionThemodernsocietydependsontheelectricitysupplymoreheavilythaneverbefore.Itcannotbeimaginedwhattheworldshouldbeiftheelectricitysupplywereinterruptedallovertheworld.Electricpowersystems(orelectricenergysystems),providingelectricitytothemodernsociety,havebecomeindispensablecomponentsoftheindustrialworld.

Section1IntroductionThefirstcompleteelectricpowersystem(comprisingagenerator,cable,fuse,meter,andloads)wasbuiltbyThomasEdison–thehistoricPearlStreetStationinNewYorkCitywhichbeganoperationinSeptember1882.ThiswasaDCsystemconsistingofasteam-engine-drivenDCgeneratorsupplyingpowerto59customerswithinanarearoughly1.5kminradius.Theload,whichconsistedentirelyofincandescentlamps,wassuppliedat110Vthroughanundergroundcablesystem.Withinafewyearssimilarsystemswerein

Section1Introductionoperationinmostlargecitiesthroughouttheworld.WiththedevelopmentofmotorsbyFrankSpraguein1884,motorloadswereaddedtosuchsystems.Thiswasthebeginningofwhatwoulddevelopintooneofthelargestindustriesintheworld.InspiteoftheinitialwidespreaduseofDCsystems,theywerealmostcompletelysupersededbyACsystems.By1886,thelimitationsofDCsystemswerebecomingincreasinglyapparent.Theycoulddeliverpoweronlyashortdistancefromgenerators.Tokeeptransmissionpowerlosses(I2R)andvoltagedrops

Section1Introductiontoacceptablelevels,voltagelevelshadtobehighforlong-distancepowertransmission.Suchhighvoltageswerenotacceptableforgenerationandconsumptionofpower;therefore,aconvenientmeansforvoltagetransformationbecameanecessity.ThedevelopmentofthetransformerandACtransmissionbyL.GaulardandJ.D.Gibb