某kV電力系統(tǒng)繼電保護(hù)設(shè)計

某110kV電力系統(tǒng)繼電保護(hù)設(shè)計摘要：本次畢業(yè)設(shè)計的主要內(nèi)容是110kV電力系統(tǒng)繼電保護(hù)的配置，并依據(jù)繼電保護(hù)配置原理，對所選擇的保護(hù)進(jìn)行整定和靈敏性校驗，確定方案中的保護(hù)。設(shè)計分為八個章節(jié)，第三、四章是計算系統(tǒng)的短路電流，確定運行方式；第五章是各種設(shè)備的保護(hù)配置。其中變壓器保護(hù)包括保護(hù)原理分析、保護(hù)整定計算和靈敏性校驗，主保護(hù)采用的是縱聯(lián)差動保護(hù)和瓦斯保護(hù)，兩者結(jié)合做到優(yōu)勢互補(bǔ)，后備保護(hù)是復(fù)合電壓啟動過電流保護(hù)。母線保護(hù)包括保護(hù)原理分析，采用了完全電流差動保護(hù)，簡單可靠。110kV側(cè)的輸電線路采用了距離Ⅰ、Ⅲ保護(hù)，由于它的電壓等級較高，還考慮了零序電流Ⅰ、Ⅲ保護(hù)。對于發(fā)電機(jī)主保護(hù)采用了縱差動保護(hù)，后備保護(hù)采用了發(fā)電機(jī)定子繞組接地保護(hù)。關(guān)鍵詞：短路電流，整定計算，靈敏度，繼電保護(hù)，微機(jī)保護(hù)Abstract:Thistimegraduationdesignofthemaincontentsbethe110kVelectricpowersystemafterrelayprotectionofscheme,andaccordingasrelayprotectionschemeprinciple，Tochoiceofprotectioncarryoncompletecalculatewiththedelicateextentcheckout,toassuranceprojectinofprotection.鋒T不h綢e為叨d敲e煙s敘i偵g霞n虎閑i暴s緩補(bǔ)d林i掏v撥i耳d灶e叮d障烈i析n裙t褲o帝依e玻i陵g必h寨t僻很c戶h續(xù)a制p汁t娘e妻r(nóng)究,恩修c配h肥a伸p皺t澇e冬r車孩3痛求a蝕n界d樓確4過乓i續(xù)s庫譜c訊a睛l換c粗u穿l逗a信t變i販o醫(yī)n喬鳴s跑y絨s揪t命e牽m于唉o喝f擔(dān)祖s扁h授o域r盆t乎盈c遷i館r畫c尊u距i儀t仰含e薯l鼓e伯c勵t荒r誠i換c匆狠c蔑u開r捎r建e凳n獻(xiàn)t順,原瞧a瓦s免s畢u誘r較a賠n饞c震e稀察c莖i誰r系c御u再l論a攔t坡e保孫a廈虎w堡a掏y杜;系紙C愿h狹a顏p弱t陷e促r繳截5良咸i訴s妄婚p紹r步o揭t飼e棋c渠t許i茄o牲n裹撇s活c朵h們e劈m慧e泰晌w謙h惹i統(tǒng)c伯h訪晉i枝s對澤v皆a先r臭i圾o兩u獻(xiàn)s誼泛e隆q診u爸i汽p卡m六e暗n決t晨s誦.山雄A嘉m繭o打n蔑g橋測t斤h參e假m魔撲t聯(lián)r甘a御n園s進(jìn)f屑o(jì)高r柱m宮e箱r士隸p凡r咽o汗t質(zhì)e御c鐮t懶i農(nóng)o烤n民米i杏n銅c岸l啟u婚d梅e炕狼p沉r決o雞t槐e盼c故t暖i碗o伙n數(shù)孫p絲r蹄i當(dāng)n自c姑i扶p廁l芳e挖雙a及n次a側(cè)l疲y宣s迎i絲s東,渡灑p潤r家o歉t曲e根c掛t蘿i炮o賄n谷憶c警o供m天p惕l欲e膽t尊e型臣c宋a肯l示c栽u奏l(xiāng)趨a液t姥e士允a貞n蜻d乒谷d均e霧l盛i酒c瓣a酬t畫e漿蓮e狡x臟t擠e播n吉t訪穿c杯h(huán)伸e魔c蹦k蛙o歇u炮t座,景真c阿e牙n自t污r敬a掏l垮押p光r騾o含t褲e們c珍t老i們o卻n殊紀(jì)i極s非風(fēng)l格e行n足g需t鐵h柴w索a帖y策s潮重a另s張s磚o欲c鏈i寧a游t理e詞d創(chuàng)葡累d真i衣f錢f配e脹r醫(yī)e礦n賊t窮i誰a賊l秋愈p鞭r(nóng)辭o親t動e借c武t盤i衡o孟n龜僅a崇n界d厘熄g程a送s刃浪p且r計o還t鑄e權(quán)c笛t級i桑o洲n撐,愿明b態(tài)o名t買h妥仇c兼o馳m表b蠻i勤n款e循鞠t盜o妙破a蔽t罪t險a拒i五n櫻誰a斥d作v算a合n拉t遮a貞g獲e添呀t禿o蔥也w世i迫t牌h凱率e爪a鉆c深h嗎侮o猛t譯h仆e成r儲母r黃e行p秩a地i論r角,拳藍(lán)s夕p縮a鳴r貫e罷聚p抽r笛o日t妻e豬c麻t嚷i助o爬n疲北i蓄s購辟c棚o衣m岔p證o挽u汗n燙d素顛e策l凱e跑c尼t(yī)筒r鉗i幼c推授v鉆o餃l淺t獎a虹g紛e細(xì)店s阿t頃a減r核t滴賀c丙o屠n陶d倒u幻c爪t刑拒e始l欲e材c狠t悟r傷i樸c局i唇t出y卻己t宜o毒宰f柳l跑o范w構(gòu)梅p凈r另o宏t約e拌c天t靠i殲o圣n收.蘆g靜e襲n云e橡r去a蹄t凍r旁i揭x們?nèi)竘駐i專n雅e近耽p比r爆o殖t傅e究c震t儲i麗o所n掌弄i殖n改c饅l拋u寸d云e匠子p這r爆o點t悔e男c笑t艦i宋o餃n衰殃p叼r澤i圣n勢c腹i柳p刑l坊e敗穩(wěn)a辯n馬a建l臉y護(hù)s觸i妥s予,圓槍a濫d訊o買p所t灘i蠟o胡n縫毛c漲o嗓m遺p秀l喂e親t參e捷載d覆i猾f事f賺e里r拋e宵n滿t狗i召a偉l涂辛e傘l環(huán)e腿c妥t賄r窗i喊c廉鋸c悶u要r曲r鈴e蟲n涼t酷等p竄r往o祝t既e杠c磁t勞i合o笨n介,慶遇s銷i望m刮p關(guān)l徹e扎撓c多r秘e巖d短i嚴(yán)b動i志l混i鹽t斥y鎮(zhèn).佛愉T檢h階e肆叛p愧o誤w盡e禍r扒鋸l潮i濤n支e門討歷o屯f還撈t泥h品e稱及1萍1謹(jǐn)0貧匆k降V娛訴a鳳d授o檢p纖t稍e截越d鬧i屆s溫t奏a裳n殖c般e憶銀Ⅰ稱攻,燭詢Ⅲ碗早p旅r黎o僅t逃e司c倘t算i傭o舍n臟,難搞b胖e專c凱a離u克s逮e挪源o受f擾佳i差t吉扣o紋f尊料t界h認(rèn)e齒年e驕l略e辦c謙t仆r誰i壩c尿鎖v今o鎖l指t璃a淡g知e冠伯g械r啦a揪d王e眼虎b豐e傻誘h董i滑g劫h扔e限r(nóng)珍,考搭a利l兔s縫o溪賺c研o拋n愿s丘i艷d狗e潑r調(diào)a源t團(tuán)i心o移n謹(jǐn)種z哄e酸r傅o鳥遵p淘r膛e臣f奏a墳c意e犧陰e攤l恥e粉c急t晌r默i黨c如呆c寨u音r繭r辮e戀n怨t縫肝Ⅰ擠躺,牛漿Ⅲ雕奔p滾r塞o脈t路e聞c賓t砌i蓄o犧n已.舍F從o妄r銹定g俊e驗n譜e樸r繭a身t袋o寸r界躬c鑰e悲n源t甲r敘a拿l恭粱p頸r榮o膀t頭e浴c覺t撥i檢o纖n連南a殃d私o虧p盛t企e前點l朗e址n鑼g漢t味h渴w秩a洪y刊s糠延a未s騙s削o隙c際i闖a膽t校e巨d吃賄賣d茄i物f布f慌e白r丟e孩n棒t孔i蟲a國l犯降p馳r熊o稿t將e匠c喘t吊i懇o友n捉,玩窮s柔p波a娃r(nóng)嘩e芳弱p猾r騎o資t四e公c規(guī)t非i情o茄n壇宵a宅d脊o偽p綠t法e梨竟g糟e筒n常e顛r物a避t詳o宗r魚忙寒s鋼t綢a擋t串o森r疫蒸c焰o磁n堵n橫e苦c惰t揉彎g浮r薦o辮u晨n咽d凈漠p規(guī)r鍬o貴t標(biāo)e奮c躬t哄i巾o脫n坐.屈K病e冒y子w賓o撇r犁d書s殘:襯S為h手o邊r祥t撓扎c干i拆r稈c鹽u懷i繪t御還e協(xié)l交e恐c旦t花r凡i耳c感掏c貸u萬r窩r年e也n蛾t央,播哀c西o溝m筒p貧l鈔e醬t快e敵望c服a角l怖c香u參l思a愛t少i舉o瓣n窄,恭慮d野e零l屆i暈c繪a館t席e著嶄e剖x繳t植e燥n尿t碑,血偶r捉e斷l(xiāng)鎖a鈴y焰康p議r處o蠶t捉e殖c屠t翅i腳o饅n即,考速m域i屋c壽r殘o比c襯o妻m抗p山u音t礎(chǔ)e壤r勾宜p暫r過o得t烈e蜂c偶t證i屋o融n臉目壤錄HYPERLINK濕氣"圖3:輸入變量“濕氣”(成員函數(shù))為變壓器年限模型輸入變量"夫喃"圖4:輸入變量“夫喃”(成員函數(shù))為變壓器年限模型Mamdani的模糊推論方法是用來對設(shè)備的壽命估計。(1)x是和y是,或x是和y是,在此是關(guān)聯(lián)的含義.如果x是及y是，然后z是(2)x表示濕氣,y表示夫喃系作為輸入(變量)和z為變壓器的老化程度而且是輸出變數(shù)。,,表現(xiàn)他們各自的功能。規(guī)則范圍限定在:AND(3)在模糊設(shè)置中，是x在的全體值集合而是y在的全體值集合。輸出變數(shù)"年限"圖5:輸出變量年限(成員函數(shù))綜上所述由于易受影響的輸出量(設(shè)備壽命)，地心引力運算法則集中用來計算區(qū)域Ai和中心區(qū)域每元函數(shù)(MF)的mi.(4)在此：(5)(6)使用上面的模型,易受影響的輸出量既變壓器壽命是關(guān)于濕氣和夫喃系的已被確定和描述在了圖6中.圖6:變壓器年限模型,以濕氣和夫喃系當(dāng)做輸入變量為基礎(chǔ)V.壽命延長現(xiàn)有變壓器數(shù)量的壽命延長是一個重要實效的議題。有足夠的安全性和涉及操作老化單位方面的環(huán)境風(fēng)險接近外面的監(jiān)視和評估的載入極限。利用正確及時的評估可以控制老化過程,RCM申請和適當(dāng)?shù)牟僮鳂?biāo)準(zhǔn)落實了廣大的剩余壽命與可接受的安全性和可改良的可靠性能達(dá)到比較好的有成本效益的利用。經(jīng)典的診斷用現(xiàn)實做解釋，因此RCM對設(shè)備延長壽命是至關(guān)重要的。通過貫徹適當(dāng)?shù)牟僮鳂?biāo)準(zhǔn)(動力載荷)可以改良現(xiàn)有老化設(shè)備的利用和有效率的/有效的維護(hù)對維持/升級絕緣系統(tǒng)。由于它在強(qiáng)調(diào)失敗結(jié)果方面定義了失敗的問題根源，利用RCM能完成比較好的結(jié)果。如圖7流程圖中所表示，利用RCM可以有效地實現(xiàn)設(shè)備延長壽命.RCM有助于經(jīng)濟(jì)有效的維護(hù)，方便操作,增強(qiáng)安全性而且減少環(huán)境的風(fēng)險。基于在線監(jiān)聽和診斷,倘若可能壽命延長的RCM策略能被比較好實現(xiàn)。-設(shè)備的關(guān)鍵部件和他們各自的功能已經(jīng)完全已知。-設(shè)備的可能故障和他們的結(jié)果包括所有的系統(tǒng)已知已知，如輸出變量,被迫的儲運損耗(中斷),收入,修理,再磨光,替換費用、安全和環(huán)境的∕連帶損害。圖7:變壓器壽命延長和管理流程圖VI.總結(jié)利用輸入變量的濕氣和呋喃化合物模糊模型可以預(yù)測紙包裝變壓器使用年限。壽命判斷將有助于最大化實現(xiàn)可實行的操作效率。系統(tǒng)可靠性和設(shè)備實用性能被確保，通過改良系統(tǒng)性能。過早的故障風(fēng)險能被最小化。設(shè)備及時的翻新、替換或再布置能被規(guī)劃。正確的操作和維護(hù)策略能被改進(jìn)和貫徹以得到最大的回報。間接的和環(huán)境的損害能被有效地最小化。PowerTransformerAgingandLifeExtensionAbstract-Powertransformerisacriticalandexpensiveassetforanypowerutility.Manytransformersaroundtheworldareservingclosetoorbeyondtheirdesignedlie.Thereisanincreasingfocusonmaintenanceandlieextensionofexistingtransformerstomaximizethereturnoninvestment.Transformerfailurestatisticsexhibitthatmostofthefailureshaveoccurredbeforereachingtheirratedlife.Transformerfailuresduetodielectricproblemsarereportedashighas75%.Furnacecompoundspresenceinoilprovideanindicationofsoliddielectricdeterioration.Itisimportanttoidentifythedeteriorationstagesofdielectricsanditsdegreeofsensitivitytowardsaging.Ageingisalsostronglydependentontemperature,oxygenandwaterlevelsinthetransformer.Thetransformerlifecanbemaximizedbycontrollingthesevariables.Thispaperpresentsafuzzylogicbasedapproachtoestimatetheageofapowertransformerusingkeyindicatorssuchasmoistureandfurnacecompounds.IndexTerms-TransformerAgeAssessment,LifeExtension,ReliabilityⅠ.INTRODUCTIONPowertransformer'sagingpopulationhasreachedacriticallevel.Existingassetsthatareclosetotheirexpectedlifearebeingconsideredforfurtherutilizationinordertoreducecapitalexpenditureasthereplacementcostofthesetransformersistoohigh.Sincemanyofthesetransformersareoperatingbeyondtheirratedlife,assetreliabilityunderpeakloadcan'tbeensured.Transformerfailuresareincreasinginnumberandhavingseriousimpactonforcedoutages,blackouts,revenueandenvironment.Transformerinsulationdegradation,acceleratedagingandcatastrophicfailuresoccurduetomanyreasonssuchasextremeoperationalconditions,adverseambientconditions(hightemperatureandhumidityindex),throughfaults,surges(switching/lightning)andgeomagneticstorms.Transformeragingisalsoaccelerated.duetolackofmaintenanceandproperfaultdiagnosis.Thedegradationofinsulationsystemisaccompaniedwiththephenomenonofchangingphysicalparametersoritsbehavior.Insulationpaperandoildegradationproducemoistureandfiurnacewhichareresponsiblefornormalandacceleratedaging.Gasesarereleasedintheinsulationsystemduetooverheating,partialdischarge(PD)andarcing.Also,thepresenceofmoistureplaysanimportantroleinthedegradationandfailureofinsulationchain.Watercontentanditsmovementbetweencelluloseandoilistemperaturedependent.Constantmonitoringoffaultgases,hotspottemperatureandwatercontent(WC)helpsindetectingfaultstypes,intensityand,uptoagoodextent,itslocation.Thermalconditionmonitoringoftransformer(includingloadtapchanger)standsvitalfortransformeroperationalplanninginparticularatpeakloadandatemergencyloading.Acceleratedagingoccursduetoincreaseinmoistureandoxygenlevelintheoil.Moistureandoxygenlevelsaretemperaturedependentandincreasewiththeincreaseintemperaturehumidityindex(THI).Higherlevelofmoistureandoxygencanleadtoabubbleformationthatcancausecatastrophicfailure.Increasedreliabilityofatransformerrequiresanoperationalcriterionthatisbasedonacceptablemoisturelimitsaccordingtoloadandtemperature.Itisvitaltoidentifythesourcesofgassingwiththeirrespectiveseverityandimpactontheassetremnantlife.Dissolvedgasanalysis(DGA)withaccurateinterpretationisoneofthemethodsforidentifyingthetypeandseverityofthefault.OnlineDGA,PDanddiagnosticssuchasfrequencyresponseanalysis(FRA)forwindingmovement,recoveryvoltagemeasurement(RVM)areimportanttoestablishasset'soverallintegrity.Transformerdiagnosticsandmonitoringdataareimportanttodecideontheoperationalcriteria,assetmanagementandreliabilitycenteredmaintenance(RCM)strategiesforlifeextension.Betterassetmanagementcanbeachievedwithon-lineconditionmonitoringandeffectivediagnostics.Endoflifeassessmentwithaccuracyisessentialforanassettoserveforitsextendedlife.Ⅱ.TRANSFORMERAGINGItisdifficulttodeterminetheasset'sconditionandagingprocessasitinvolvesmanyvariablesactingatthesametimeinacomplexmanner.Theagingprocessintheoil/celluloseinsulationsystemunderthermalstressandtheirmeasurableeffectsareduetochemicalreactionsintheinseparabledielectricsystem.Thedielectrictemperatureisacriticalagingparameterthatcausesachangeinthemechanicalandelectricalpropertiesofthematerial.Paperinsulationiscomposedofapproximately40%cellulose.DegreeofPolymerization(DP)isameasurementofaveragenumberofglucoseunitspermolecularchain.Paperinsulation,withDPgreaterthan1000,exhibitshighdielectricandtensileproperties,whereasDPvaluelessthan300showsapaperwithpoordielectricandmechanicalproperties.Presenceofwaterandoxygenintheinsulationsystemacceleratestheagingphenomenon.Moistureisagoodindicatortodeterminetheaging,reliabilityandsafetyofthetransformer.Hydrolysis,PyrolysisandOxidationarethethreemechanisms,actingsimultaneously.Theagingmechanismaffectstheelectricalandmechanicalpropertiesofthedielectrics.111.ENDOFLIFEASSESSMENTResiduallifeofidenticaltransformers,withsameperiodofservice,mayvarybecauseofitsinsulationbehavior.Insulationbehaviordependsontemperature,moisturecontentandoxygeningress.Operatingenvironment(altitude,ambientconditions,sunshineandairflow),dynamicloading,systemimpedance,switchingandlightingsurges(overvoltages),throughfaultsandcontaminationsarethemajorfactorstowardsasset'sacceleratedaging.Economicandendoflifeassessmentareessentialfortheexistingagedassetstoplanforthemaintenance,relocationorretirement.Furnacecompoundandmoisturecontentsarethekeyindicatorsforlifeassessment.Furnacecompoundsaregeneratedduetoinsulatingpaper(cellulose)degradationwithnormalagingaswellasduetoincipientfaults.Duetodegradationprocess,papertensileanddielectricstrengthdecreases.Electromagneticforcesduetothroughfaultcurrenthaveseriousimpactonthepaperlifebyloweringitstensilestrength.Goodcorrelationcanbeobtainedbetweenfurnacecompoundanddegreeofpolymerization(DP).Thereforethefurnacecompoundquantitypresentintheoilisagoodindicatorforlifeassessment.ThetransformeragecharacteristicsbasedonfurnacecompoundpresentindifferentagegroupsisshowninFigure1.REMNANTLIFE(YEARS)Figure1TransformeragingcharacteristicwithrespecttoFuran(C4H4O).Furanincreasesduetoinsulationdegradationwithage.Furansaregeneratedduetooverallriseintemperatureaswellasduetotheheatproducedbyactivefaultinanylocalizedarea.Basedontheanalysis,assetcouldbeidentifiedforfuransproducedduetonormalagingorlocalizedfault.Assetoperatingwithpoorpaperstrengthmayresultincatastrophicfailurewithseriousthreattoenvironmentandcollateraldamages.Tomonitorthepaperdegradationtrend,Furananalysiscanplaykeyroleintheoverallassessment.Itisaveryusefuldiagnosticforassessingwhetherafailedtransformershouldberepaired,rewoundorscrapped.Temperature,oxygenandmoisturearethekeyfactorsinacceleratingtheagingprocess.Operatingtemperatureandambienttemperatureexiststhroughoutthelifeofthetransformer,affectingtheinsulationlife.Studiesandfieldexperienceshowthatgradualincreaseintemperaturereducesthepeakloadinsulationlifeoftheasset.Ariseof7°Celsiusabovenormaloperatingtemperaturedecreasesasset'slifeby50%.Moisture(watercontent)ininsulationchainisproducedduetothermo-kineticdegradationofthepaperaswellagingoftheoil.Moisterpresentintheatmospherepenetratesthroughweaksealantwiththechangeinthepressuregradient.Thewatersolubilityinthetransformermineraloilincreaseswiththeincreaseintemperature.Themoistureinfluencesthedecompositionofthemolecularchain,acceleratesthecelluloseagingprocess,affectingthetensileanddielectricpropertiesoftheinsulationsystem.Dielectricbreakdownstrengthdecreaseswithincreaseinmoisture.Basedonthemoisturepresenceintheinsulationchain,transformerriskassessmentisessentialforitseffectivelifeextensionandbetterassetmanagement,Table1.TABLEIMOiSTURELEVELSANDTRANSFORMERFAILURERISKZONESInsulationAverageMoistureContentAssessment4%EnteringFiskZone5%—6%ConsiderableFailureRisk7%FailureImminentMoistureisexchangedbetweenpaperandoilanditsdynamicsarehighlytemperaturedependent.Moisturedynamicsfrompapertooilincreaseswithincreaseinthetemperature,butwiththedecreaseintemperaturethemoisturemovesbacktothepaperslowly.ThestandardmethodformeasuringthemoistureinoilisKaralFischerreactiontest(ASTMD1533).Thistestishighlyrecommendedandiswidelyusedduetoitshighselectivityandsensitivity.Watercontentintheinsulationsystemshouldbekepttoaminimumtomaintaintherequireddielectricproperties.Thetransformeragecharacteristicsbasedonmoisturecontents,presentindifferentagegroupsisshowninFigure2.REMNANTLIFE(YEARS)Figure2:TransformeragingcharacteristicswithincreaseinmoistureContentduetoagingandthermo-kineticdegradation.IV.LIFEESTIMATIONMODELUSINGFUZZYLOGICUsuallyfuranandmoisturearegeneratedsimultaneouslyinaverycomplexmannerandarekeyfactorsinidentifyingasset'sremnantlife.Presenceofbothhasseriousimpactontheassetperformanceandlife,ignoringonecouldmisleadtheestimation.Thefuzzylogicmodelingandanalysishasbeencarriedouttogetbetterasset'sremnantlifeestimation.Figure3&4representsthemoistureandfuransasinputvariablesforthelifeestimationfuzzylogicmodel.Figure5representstheasset'sageasanoutputvariableofthemodel.Inputvariable“Moisture”Figure3:Inputvariable“Moisture”(membershipfunctions)fortransformeragemodelInputvariable“Furan”Figure4:Inputvariable“Furan”(membershipfunctions)fortransformeragemodelMamdani'sfuzzyinferencemethodisappliedtoestimatetheasset'slife.(1)Wherexisandyis,orxisandyisandsoonasaconjunctionofimplications.IFxisANDyis，THENzis(2)Wherexrepresentsthemoisture,yrepresentsfuranasinputs(variables)andztheageofthetransformerandistheoutputvariable.,thenrepresenttheirrespectivemembershipfunctions.Theextenttowhicharuleisactivated:AND(3)Whereisthemembershipvalueofxinthefuzzysetandisthemembershipvalueofyinthefuzzyset.outputvariable“Age”Figure5:outputvariableage(membershipfunctions)Defuzzificarion:Forcrispoutput(assetlife),centerofgravityalgorithmisusedtocalculatetheareaAiandcenterofareaMiforeachmemberfunction(MF).(4)Where:(5)(6)Usingtheabovemodel,thecrispoutput"transformerage"withrespecttomoistureandfuranisdeterminedandisrepresentedinFigure6.Figure6:transformeragemodel,basedonmoistureandFuranasinputvariablesV.LIFEEXTENSIONLifeextensionofexistingtransformerpopulationisanimportantissuefortheutilities.Thereisanamplesafetyandenvironmentalriskinvolvedinoperatingagedunitsclosetoloadinglimitswithoutsurveillanceandassessment.Agingprocesscanbecontrolledwithaccurateintimeassessment,RCMapplicationandproperoperationalcriteriaimple