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河南理工大学万方科技学院本科毕业论文

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外文资料与中文翻译

外文资料：

SelectionandCoolingofPowerTransformer

Theselectionofthetransformercanhaveamajorimpactonthe

costofasubstation,sincethetransformerrepresentsthemajorcost

item.Nameplateratingisonlyaguidetotransformerapplication,and

shouldonlybeusedasafirststepintheselectionprocess.The

transformerisavailableasaself-cooledunit,oritcanbepurchased

withadditionalstepsofforcedcoolingthatusefanorfansandoil

pumps.Thenameplateratingscanbeincreasedfrom25%to66%bythe

additionoffanspumps.Thenameplateratingisbasedonacontinuous

00

loadproducinga55Cto65Cconductortemperatureriseoverambient.

Sincemanytransformersdonotcarrycontinuousloads,advantagecan

begainedfromthethermaltimelagtocarryhigherpeakloadswithout

exceedingthetemperaturelimits.Transformerratingsarebasedon

theassumptionthatonlyanextremelyslowdeteriorationof

insulationwilltakeplacewithnormaloperation.Asubstantial

increaseinratingcanbeachievedbyacceleratingthelossof

insulationlife,Thisincreaseinratingmightapproach200%foran

hourortwo,andapproximately120%for24hours.Forsubstationsthat

aredesignedtocarryfullloadundertheoutageofanyonetransformer,

ahighemergencyratingfora24-hourperiod(e.g.Untilthefailed

unitcanbereplaced)couldmeantheselectionofsmallertransformer

河南理工大学万方科技学院本科毕业论文

andasubstantialsavinginsubstationcost.

Theselectionofthetransformershouldinvolveacareful

evaluationofanumberofotherfactors:

(1)Impedances