毕业设计供配电类英文原文

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1、附录二：英文原文ElectricpowerdistributionAnelectricpowerdistributionsystemisthefinalstageinthedeliveryofelectricpower;itcarrieselectricityfromthetransmissionsystemtoindividualconsumers.Distributionsubstationsconnecttothetransmissionsystemandlowerthetransmissionvoltagetomediumvoltagerangingbetween2k

2、Vand35kVwiththeuseoftransformers.Primarydistributionlinescarrythismediumvoltagepowertodistributiontransformerslocatednearthecustomer'spremises.Distributiontransformersagainlowerthevoltagetotheutilizationvoltageofhouseholdappliancesandtypicallyfeedseveralcustomersthroughsecondarydistribution

3、linesatthisvoltage.Commercialandresidentialcustomersareconnectedtothesecondarydistributionlinesthroughservicedrops.Customersdemandingamuchlargeramountofpowermaybeconnecteddirectlytotheprimarydistributionlevelorthesubtransmissionlevel.HistoryFurtherinformation:Historyofelectricpowertransmiss

4、ionElectricpowerdistributiononlybecamenecessaryinthe1880swhenelectricitystartedbeinggeneratedatpowerstations.Beforethatelectricitywasusuallygeneratedwhereitwasused.ThefirstpowerdistributionsystemsinstalledinEuropeanandUSciteswereusedtosupplylighting:arclightingrunningonveryhighvoltage(usual

5、lyhigherthan3000volt)alternatingcurrent(AC)ordirectcurrent(DC),andincandescentlightingrunningonlowvoltage(100volt)directcurrent.Bothweresupplantinggaslightingsystems,witharclightingtakingoverlargearea/streetlighting,andincandescentlightingreplacinggasforbusinessandresidentiallighting.Duetot

6、hehighvoltagesusedinarclighting,asinglegeneratingstationcouldsupplyalongstringoflights,upto7-mile(11km)longcircuits,sincethecapacityofawireisproportionaltothesquareofthecurrenttravelingonit,eachdoublingofthevoltagewouldallowthesamesizecabletotransmitthesameamountofpowerfourtimesthedistance.

7、Directcurrentindoorincandescentlightingsystems(forexamplethefirstEdisonPearlStreetStationinstalledin1882),haddifficultysupplyingcustomersmorethanamileawayduetothelow110voltsystembeingusedthroughoutthesystem,fromthegeneratorstothefinaluse.TheEdisonDCsyste