电气专业毕业设计外文材料及翻译.docx

电气专业毕业设计外文材料及翻译.docx

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中英文翻译

专业：

电气工程及其自动

化

姓名：

唐晓

学号：

0628010132

指导老师：

易晓郑

2010年5月28日

PowerSystemPlanning

Inanticipationofcontinuedgrowthintheloadsservedbytheelectricntilities,powersystemsmustbecontinuallyexpandedincapability.Long-rangeplanningisessentialtoassurethatnecessaryadditionsaretechnicallyadequate,reasonableincostandfitintoagrowthpattern.Thedifficultiesencounteredbythelong-rangedplannerinclude:

uncertaintyofloadgrowthwithrespecttobothgeographyandtime,theprobabilityofnewinwentionortechnologicaldevelopment.Goodsystemplanningstrivesforoptimumdesignonasystem-widebasis,notnecessarilyforminimumcostinonepartofthesystemwithoutregardtotheeffectontheotherparts.Inrecentyears,therehasbeenanemphasisoneconomyinplanningandoperation.Nowthereisincreasedemphasesonreliabilityandenvironmentalfactors.

Beforeplanningdecisionsaremade,manyfactorsmustbecarefullyconsidered:

（1）Equipmentdecisionhavelong-termeffectsrequiringaforecastandstudyperiodof15-25years.

（2）Therearemanyalternatemeansofgeneratingelectricpower:

nuclear,base-loadfossil,mid-rangecombustionturbinesorhydro,andinlarge,medium,orsmall-sizeplants,anddifferentformsofenergystorage.

（3）Thereareseveralalternatemeansoftransmittingelectricpower,forexample,byalternatingordirectcurrrent

overheadorundergroudcable,andalloverawiderangeofvoltages.

（4）Theplanningdecisionsareaffectedbyloadmanagementtechniquesandtheloadpatterns.

（5）Uncertaintyexistsconcerningthefactors,suchasfuturefuelcosts,interstratesonmoneyandcapitalavailability,equipmentforced-outagerates,newtechnologiesandenvionmentalrestrictions.

ElectricPowerSystemMonitoring

Amodernelectricpowersystemisanassemblyofmany

components,eachofwhichinfluencesthebehaviorofeveryotherpart.Properfunctioningofthesystemasawholemakesitnecessarytomonitorconditionsexistingatmanydifferentpointsonthesysteminordertoassureoptimumoperation.

Theconcernofthecustomersisprimarilythatthefrequencyandvoltageofthesupplyareheldwithincertainrathernarrowlimits.Sincefrequencyofthesystemisthesameeverywhere,itmaybemonitoredbyasinglefrequencymeterlocatedatanyconvenientpoint.Incontrast,thevoltageofthesystemmaybequitedifferentatdifferentpoints.Consequently,itisnecessarytomakecontinuousobservationofthevoltageatcertainkeypointsinthesysteminordertoprovideacceptableservice.

Efficientoperationofthesystemisobtainedbyassigningproperloadschedulestoeachofthegeneratorsofthesystem.Newerplants,althoughindividuallymoreefficient,maybelocatedatpointsofthesystemwheretheirloadingoccasionslargesystemlosses.Itisdesirabletooperatewithsuchadivisionoftheloadbetweengeneratorsthatthetotalcostoffuelconsumedisminimized.Toprovidereliabilityofthepowersupplyineventofunexpectedconditions,itisdesirableforallmachinesinoperationtohavethetotalkilowattratingsomewhatgreaterthanthetotalloadpluslosses.

Instrumentationisnecessarytopermitbilllingofcustomersforenergyused.Manyinterconnectionsexistbetweendifferentpowersystems.Instrumentsmustbeprovidedatinterchangepointstopermitbillingforenegytransferredfromonesystemtoanther.Thecontinuousmonitoringofenergytransferinnecessarytoassurethatinterchangedpoweriswithinthelimitsofcontractagreements.

Thecontinuousmeasurementofconditionsofmajorpiecesofequipmentisnecesserytoavoiddamageduetooverload.Instrumentationservesanaguideforfutureconstructioninagrowingpowersystem.

Occasionally,underemergencyconditions,asystemoperatorobservesthathissystemloadexceedstheabilityoftheavailablegeneratingandtransmissionequipment.Heisthenfacedwiththeproblemofloadsheddingor,moreproperly,loadconservation.Itisthennecessarytodropselectedloadswhereserviceinterruptionisleastobjectionable.Insuchanevent,hereliesonthemanyinstrumentswhichprovideinformationrelativetosystem-operation

conditions.

Instrumentsmaysoundalarmsasadvancewarningsofconditionsrequiringactiontoavoiddamagetoequipmentoperatingbeyonditsdesignlimitation.Intheeventofextremeconditionssuchaspower-systemfaults,defectiveequipmentisswitchedoutofserviceautomatically.Instrumentsthatcontinuouslymonitorcurrent,voltage,andotherquantitiesmustbeabletoindentifythefaultedequipmentandtobringaboutoperationofthecircuitbreakerswhichremoveitfromservice,whileleavinginserviceallotherequipmentontheoperatingsystem.

Themanydifferentelectricaldevicesinapowersystemandthoseownedbythecustomersaredesignedforop