电气专业毕业设计外文材料及翻译Word文档下载推荐.docx
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电气专业毕业设计外文材料及翻译Word文档下载推荐.docx
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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
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