變壓器勵(lì)磁涌流的抑制變壓器勵(lì)磁涌流不僅導(dǎo)致繼電保護(hù)誤動(dòng)，由其衍生的電網(wǎng)電壓驟降、諧波污染、和應(yīng)涌流、鐵磁諧振過電壓等都給電力系統(tǒng)運(yùn)行帶來不可低估的負(fù)面影響。數(shù)十年來人們通過識(shí)別勵(lì)磁涌流特征的方法來減少繼電保護(hù)的誤動(dòng)率，但并未獲得良好的回報(bào)，誤動(dòng)率仍居高不下。至于對(duì)電壓驟降、諧波污染、和應(yīng)涌流等的消除更一籌莫展。究其原因是人們認(rèn)為勵(lì)磁涌流的出現(xiàn)不可抗拒，只能采用“識(shí)別”的對(duì)策，即“躲”的對(duì)策。其實(shí)，換個(gè)思路一一“抑制”，是完全可以實(shí)現(xiàn)的，而且已經(jīng)實(shí)現(xiàn)了。引言變壓器勵(lì)磁涌流與電容器的充電涌流抑制原理完全相似，電感及電容都是儲(chǔ)能元件，前者不容許電流突變，后者不容許電壓突變，空投電源時(shí)都將誘發(fā)一個(gè)暫態(tài)過程。在電力變壓器空載接入電源時(shí)及變壓器出線發(fā)生故障被繼電保護(hù)裝置切除時(shí)，因變壓器某側(cè)繞組感受到外施電壓的驟增而產(chǎn)生有時(shí)數(shù)值極大的勵(lì)磁涌流。勵(lì)磁涌流不僅峰值大，且含有極多的諧波及直流分量。由此對(duì)電網(wǎng)及電器設(shè)備造成極為不利的影響。1、 勵(lì)磁涌流的危害性1.1引發(fā)變壓器的繼電保護(hù)裝置誤動(dòng)，使變壓器的投運(yùn)頻頻失?。?.2變壓器出線短路故障切除時(shí)所產(chǎn)生的電壓突增，誘發(fā)變壓器保護(hù)誤動(dòng)，使變壓器各側(cè)負(fù)荷全部停電；1.3A電站一臺(tái)變壓器空載接入電源產(chǎn)生的勵(lì)磁涌流，誘發(fā)鄰近其他B電站、C電站等正在運(yùn)行的變壓器產(chǎn)生“和應(yīng)涌流”(sympatheticinrush)而誤跳閘，造成大面積停電；1.4數(shù)值很大的勵(lì)磁涌流會(huì)導(dǎo)致變壓器及斷路器因電動(dòng)力過大受損；1.5誘發(fā)操作過電壓，損壞電氣設(shè)備；1.6勵(lì)磁涌流中的直流分量導(dǎo)致電流互感器磁路被過度磁化而大幅降低測(cè)量精度和繼電保護(hù)裝置的正確動(dòng)作率；1.7勵(lì)磁涌流中的大量諧波對(duì)電網(wǎng)電能質(zhì)量造成嚴(yán)重的污染。1.8造成電網(wǎng)電壓驟升或驟降，影響其他電氣設(shè)備正常工作。數(shù)十年來人們對(duì)勵(lì)磁涌流采取的對(duì)策是“躲”，但由于勵(lì)磁涌流形態(tài)及特征的多樣性，通過數(shù)學(xué)或物理方法對(duì)其特征識(shí)別的準(zhǔn)確性難以提高，以致在這一領(lǐng)域里勵(lì)磁涌流已成為歷史性難題。2、 勵(lì)磁涌流的成因抑制器的重要特點(diǎn)是對(duì)勵(lì)磁涌流采取的策略不是“躲避”，而是“抑制”。理論及實(shí)踐證明勵(lì)磁涌流是可以抑制乃至消滅的，因產(chǎn)生勵(lì)磁涌流的根源是在變壓器任一側(cè)繞組感受到外施電壓驟增時(shí)，基于磁鏈?zhǔn)睾愣ɡ?，該繞組在磁路中將產(chǎn)生單極性的偏磁，如偏磁極性恰好和變壓器原來的剩磁極性相同時(shí)，就可能因偏磁與剩磁和穩(wěn)態(tài)磁通疊加而導(dǎo)致磁路飽和，從而大幅度降低變壓器繞組的勵(lì)磁電抗，進(jìn)而誘發(fā)數(shù)值可觀的勵(lì)磁涌流。由于偏磁的極性及數(shù)值是可以通過選擇外施電壓合閘相位角進(jìn)行控制的，因此，如果能掌握變壓器上次斷電時(shí)磁路中的剩磁極性，就完全可以通過控制變壓器空投時(shí)的電源電壓相位角，實(shí)現(xiàn)讓偏磁與剩磁極性相反，從而消除產(chǎn)生勵(lì)磁涌流的土壤——磁路飽和，實(shí)現(xiàn)對(duì)勵(lì)磁涌流的抑制。長期以來，人們認(rèn)為無法測(cè)量變壓器的剩磁極性及數(shù)值，因而不得不放棄利用偏磁抵消剩磁的想法。從而在應(yīng)對(duì)勵(lì)磁涌流的策略上出現(xiàn)了兩條并不暢通的道路，一條路是通過控制變壓器空投電源時(shí)的電壓合閘相位角，使其不產(chǎn)生偏磁，從而避免空投電源時(shí)磁路出現(xiàn)飽和。另一條路是利用物理的或數(shù)學(xué)的方法針對(duì)勵(lì)磁涌流的特征進(jìn)行識(shí)別，以期在變壓器空投電源時(shí)閉鎖繼電保護(hù)裝置，即前述“躲避”的策略。這兩條路都有其致命的問題，捕捉不產(chǎn)生偏磁的電源電壓合閘角只有兩個(gè)，即正弦電壓的兩個(gè)峰值點(diǎn)（90°或270°），如果偏離了這兩點(diǎn)，偏磁就會(huì)出現(xiàn)，這就要求控制合閘環(huán)節(jié)的所有機(jī)構(gòu)（包括斷路器）要有精確、穩(wěn)定的動(dòng)作時(shí)間，因?yàn)槿鐒?dòng)作時(shí)間漂移1毫秒，合閘相位角就將產(chǎn)生18。的誤差。此外，由于三相電壓的峰值并不是同時(shí)到來，而是相互相差120°，為了完全消除三相勵(lì)磁涌流，必須斷路器三相分時(shí)分相合閘才能實(shí)現(xiàn)，而當(dāng)前的電力操作規(guī)程禁止這種會(huì)導(dǎo)致非全相運(yùn)行的分時(shí)分相操作，何況有些斷路器在結(jié)構(gòu)上根本無法分相操作。用物理和數(shù)學(xué)方法識(shí)別勵(lì)磁涌流的難度相當(dāng)大，因?yàn)閯?lì)磁涌流的特征和很多因素有關(guān)，例如合閘相位角、變壓器的電磁參數(shù)等。大量學(xué)者和工程技術(shù)人員通過幾十年的不懈努力仍不能找到有效的方法，因其具有很高的難度，也就是說“躲避”的策略困難重重，這一策略的另一致命弱點(diǎn)是容忍勵(lì)磁涌流出現(xiàn)，它對(duì)電網(wǎng)的污染及電器設(shè)備的破壞性依舊存在。圈2T變壓器示意圖圖2-1為一單相變壓器結(jié)構(gòu)圖，可寫出空載時(shí)初級(jí)繞組的電壓方程竺ul=ilRl+Nl出 （2.1）式中N1、R1分別為初級(jí)繞組的匝數(shù)及電阻施U觀濕（俸+皮）=iiAi+^1-^—（2.1）可改寫為式中a為t=0時(shí)U1的初相角如忽略電阻R1，即（2.3）設(shè)R1=0，則得求解（2.3）式微分方程得磁通0的表達(dá)式為中=_^次勰+南+1*Ni （2.4）依據(jù)磁鏈?zhǔn)睾愣ɡ?，合閘瞬間磁路中磁鏈不能突變，即可求出積分常數(shù)C。C=^-Cosa成1 （2.5）式中中=S^［Cosa-Cos（^+切］①Ni y二中潴勰+O1）］ （2.6）可寫出磁通0表達(dá)式中=』式中苗泌為總磁通的幅值從式（2.6）中不難看出變壓器外施電壓u1在不同初相角a合閘時(shí)所產(chǎn)生的磁通0都不相同，將式（2.6）改寫為=^mCasa-^mCas{a^+ar）_Cy?- 曰式（2.7）中為暫態(tài)磁通，即偏磁，在合閘瞬間0p的值與。有關(guān)，在90°或270°空投時(shí)Cy?=^mCasa0p=0，在0°或180°空投時(shí)0p可達(dá)峰值0m。式（2.7）中 為穩(wěn)態(tài)磁通，為一周期函數(shù)。圖2-2為空投合閘角a=0時(shí)的磁通變化曲線，圖中0s為穩(wěn)態(tài)磁通，0為0s和0p合成的總磁通（未計(jì)及剩磁0res），0sat為變壓器飽和磁通。對(duì)于無損變壓器（R1=0）偏磁0p不會(huì)衰減，如實(shí)線所示，對(duì)于有損變壓器（R1>0）

It勵(lì)礁誦（Hi體總磁通心恂和磁通制磁心㈤匿吃舍前角隊(duì)面的通1變化曲蛇It勵(lì)礁誦（Hi體總磁通心恂和磁通制磁心㈤匿吃舍前角隊(duì)面的通1變化曲蛇總暖通5（R>0）哲酒廄通小P〔雎口）暫瘩廄通巾r〔R網(wǎng)）/f.■一剝障心〔正LiT=—0p按時(shí)間乩常數(shù)衰減，如虛線所示。從卸-2中可看出在電壓相位角在。1至02區(qū)間總磁通0大于飽和磁通0sat，磁路飽和，因而產(chǎn)生勵(lì)磁涌流iy，iy具有間斷性。對(duì)于無損變壓器中和iy是關(guān)于’=懿+女=”的偶對(duì)稱波形，而在iy=0的間斷角區(qū)間0則是關(guān)于°=2汗的偶對(duì)稱波形。對(duì)于有損變壓器則0與iy將不再有對(duì)稱關(guān)系。當(dāng)計(jì)及剩磁時(shí)，總磁通將由剩磁、偏磁（暫態(tài)磁通）及穩(wěn)態(tài)磁通三者組成。不難看出在圖2-2偏磁的情況下，如剩磁為正，則總磁通曲線向上平移，即磁路更易飽和，勵(lì)磁涌流幅值會(huì)更大。如剩磁為負(fù)，則勵(lì)磁涌流將被抑制。圖03圖03鐵磁材料的磁滯回蛙*圖2-3是鐵磁材料的磁滯回線，它描述在磁路的勵(lì)磁線圈上施加交流電壓時(shí)，磁勢(shì)H也相應(yīng)的從-Hc到Hc之間變化，由H產(chǎn)生的磁通6（或磁通密度B=0/S）將在磁滯回線上作相應(yīng)的變化。如果H在回線上的某點(diǎn)突然減到零，則B將隨即落到對(duì)應(yīng)B軸的某點(diǎn)上，該點(diǎn)所對(duì)應(yīng)的B值即為剩磁Br?？梢钥闯鍪４诺臄?shù)值和極性與切除勵(lì)磁電壓的相位角有關(guān)，如果在第1、11象限切斷勵(lì)磁電源（即H=0）則剩磁為正或零，在III、W象限切斷勵(lì)磁電源，則剩磁為負(fù)。3、勵(lì)磁涌流的抑制方法變壓器在正常帶電工作時(shí)，磁路中的主磁通波形與外施電源電壓的波形基本相同，即是正弦波。磁路中的磁通滯后電源電壓90°，通過監(jiān)測(cè)電源電壓波形實(shí)現(xiàn)對(duì)磁通波形的監(jiān)測(cè)，進(jìn)而獲取在電源電壓斷電時(shí)剩磁的極性。變壓器空投上電時(shí)產(chǎn)生的偏磁6p也一樣，因偏磁，電源電壓上電時(shí)的初相角a在I、W象限區(qū)間內(nèi)產(chǎn)生的偏磁極性為正，而初相角a在II、III象限區(qū)間內(nèi)產(chǎn)生的偏磁極性為負(fù)。顯然，剩磁極性可知，偏磁極性可控，只要空投電源時(shí)使偏磁與剩磁極性相反，涌流即被抑制。變壓器初級(jí)電壓u、主磁通6、剩磁6Res及偏磁6p與分閘角和合閘角的關(guān)系曲線圖，以及電源電壓u分閘初相角a’與剩磁6Res的關(guān)系曲線。變壓器處于穩(wěn)態(tài)時(shí)主磁通6滯后電源電壓u90°.變壓器空載上電時(shí)所產(chǎn)生的偏磁一定與穩(wěn)態(tài)時(shí)對(duì)應(yīng)上電時(shí)電壓u曲線上電點(diǎn)的穩(wěn)態(tài)磁通大小相等，極性相反，其最大值可達(dá)穩(wěn)態(tài)磁通6的峰值6m，而剩磁6Res幅值與磁路材料的特性有關(guān)。不難看出對(duì)應(yīng)同一個(gè)合閘初相角a或分閘初相角a'所產(chǎn)生的偏磁和剩磁的極性正好相反，也就是說通過分閘時(shí)測(cè)量電源電壓分閘角a‘，并將a‘保存下來，在下次空投變壓器時(shí)選擇在合閘角a等于a‘時(shí)加上電源，偏磁就可與剩磁反向，它們的合成磁通將小于飽和磁通6sat（曲線④），（因飽和磁通一般選擇大于穩(wěn)態(tài)磁通峰值），磁路不會(huì)飽和，從而實(shí)現(xiàn)對(duì)勵(lì)磁涌流的抑制。由于三相電源電壓在斷路器三相聯(lián)動(dòng)切除時(shí)所得到的三相分閘相角各相差120°，剩磁極性也是三相各相差120°，而在三相聯(lián)動(dòng)合閘時(shí)三相的合閘初相角也是相差120°，三相偏磁極性也各相差120°，這樣就自然實(shí)現(xiàn)了變壓器三相磁路中的偏磁和剩磁都是抵消的，從而避免了一定要斷路器分相分時(shí)操作才能抑制勵(lì)磁涌流的苛求，也就是說三相聯(lián)動(dòng)斷路器支持對(duì)三相涌流的抑制。由于抑制勵(lì)磁涌流只要偏磁和剩磁極性相反即可，并不要求完全抵消，因而當(dāng)合閘角相對(duì)前次分閘角有較大偏差時(shí)，只要偏磁不與剩磁相加，磁路就不會(huì)飽和，這就大大降低了對(duì)斷路器操作機(jī)構(gòu)動(dòng)作時(shí)間的精度要求，為這一技術(shù)的實(shí)用化奠定了基礎(chǔ)。將這種抑制器與快切裝置和備自投裝置聯(lián)動(dòng)即可實(shí)現(xiàn)備用變壓器按冷備用方式運(yùn)行，這將大大節(jié)約變壓器熱備用方式的空載能耗。圖3-1選錄了四條勵(lì)磁涌流Iy與分閘角a‘和合閘角a的關(guān)系曲線，可以看到，在合閘角a為90?；?70°時(shí)，空投變壓器的勵(lì)磁涌流與變壓器的前次分閘角無關(guān)，原因是在變壓器初級(jí)電壓過峰值時(shí)上電不產(chǎn)生偏磁，不論變壓器原來是否有剩磁都不會(huì)使磁路飽和。當(dāng)然，如果使用三相聯(lián)動(dòng)斷路器是不可能做到三相的偏磁都為零。而當(dāng)合閘角a為0°或180°時(shí)則空投變壓器的勵(lì)磁涌流與前次分閘角a‘密切相關(guān)，當(dāng)a與a'相近（大約相差±60°）時(shí)勵(lì)磁涌流被抑制，此后a與a‘偏離越大，勵(lì)磁涌流也越大。由此可以看到如斷路器的合閘時(shí)間漂移在土3ms時(shí)對(duì)涌流的抑制基本無影響。當(dāng)今的真空斷路器和SF6斷路器的分、合閘時(shí)間漂移都在1ms之內(nèi)，完全可以精確實(shí)現(xiàn)對(duì)勵(lì)磁涌流的抑制。分閘角a’與合閘角a對(duì)勵(lì)磁涌流的影響曲線圖3-1應(yīng)該指出，變壓器斷電后留在三相磁路中的剩磁在正常情況下是不會(huì)衰減消失的，不會(huì)改變極性。只有在變壓器鐵心受到高于材料居里點(diǎn)的高溫作用后剩磁才會(huì)衰減或消失，但一般的電站現(xiàn)場(chǎng)不會(huì)出現(xiàn)這種情況。退一步講，剩磁消失是件好事，只要沒有剩磁，僅靠偏磁是不會(huì)引起磁路飽和的。4、結(jié)束語電力變壓器空投充電相位角與前次切除電源相位角匹配原則，從理論及實(shí)踐上都證明了在使用三相聯(lián)動(dòng)操作斷路器時(shí)能徹底抑制勵(lì)磁涌流。同樣，電力電容器空投充電相位角與前次切除電源相位角匹配原則，也能實(shí)現(xiàn)抑制三相聯(lián)動(dòng)斷路器合閘時(shí)的電容器充電涌流。這一技術(shù)對(duì)根除保護(hù)誤動(dòng)、改善電能質(zhì)量、提高運(yùn)行可靠性有重要意義。同樣對(duì)各種電壓等級(jí)電力系統(tǒng)的無功補(bǔ)償、遠(yuǎn)距離輸電線路的串聯(lián)補(bǔ)償控制等也有重要意義。TransformerinrushcurrentsuppressionTransformerinrushcurrentleadsnotonlytotheprotectiverelayingmisoperation,derivedfromthepowergridvoltagesags,harmonicpollution,andtheinrushcurrent,ferromagneticresonanceovervoltageinpowersystemoperation,tobringthenegativeeffectthatcannotunderestimate.Fordecadesthepeoplethroughtheidentificationofinrushcurrentfeaturemethodtoreducetherelaymisoperationrate,butdidnotgainagoodreturn,malfunctionrateisstillhigh.Asforthevoltagesag,harmonicpollution,andtheinrushcurrent,eliminationofthemorebenonplussedoversth..Thereasonisthatpeoplethinktheinrushcurrentappearsirresistible,canonlyuse"recognition"countermeasure,namely"hide"countermeasure.Infact,changeatrainofthought--"inhibition",canbefullyrealized,andhaveachieved.IntroductionTransformerinrushandsurgesuppressioncapacitorchargingprincipleiscompletelysimilartotheinductanceandcapacitanceareenergystoragedevices,theformerdoesnotallowcurrentmutation,whichdoesnotallowvoltagesurge,powerdropwillinduceatransientprocess.Accessinthepowertransformerno-loadtransformeroutletpowerfailureandprotectiondevicestoberemoved,becauseofasideofthetransformerwindingstofeelthesurgeappliedvoltagevaluesaresometimesgeneratedagreatinrushcurrent.Inrushcurrentpeakisnotonlylarge,andcontainsverymanyharmonicsandDCcomponent.Electricalequipmentonthegridandthusresultinanextremelynegativeimpact.thedangerofinrushcurrentcausedbythetransformerprotectiondevicesmalfunction,thefrequentfailureofthetransformerandputintooperation;removalofthetransformershort-circuitfaultoutletvoltagegeneratedwhenthesuddenincreaseintheprotectioninducedbytransformermalfunction,sothateachsideofthetransformerloadallthepower;Apowerstationaccesstoapowertransformerno-loadinrushcurrentgenerated,inducingotherBpowerstationnearby,Cpowerstationtransformersarerunninga"andshouldsurge"(sympatheticinrush)andfalsetripping,resultinginalargeareapowerfailure;largeinrushcurrentvalueofwouldresultinelectricpowertransformersandcircuitbreakersduetoexcessivedamage;1.5-inducedover-voltage,damagedelectricalequipment;inrushcurrentoftheDCcomponentleadtoover-currenttransformermagnetizationandmagneticsignificantlyreducethemeasurementaccuracyandthecorrectactionrateofprotectiondevices;magnetizinginrushcurrentinalargenumberofharmonicsonpowerqualitycausedbypollution.causedbyvoltagesagsorswells,affectingthenormaloperationofotherelectricalequipment.Fordecades,peoplehavetakentotheinrushcurrentapproachisto"hide”,butbecauseofinrushcurrentformandcharacteristicsofdiversity,throughmathematicalorphysicalmethodstoidentifyitscharacteristicsdifficulttoimprovetheaccuracyofthatinrushcurrentinthisfieldhasbeenahistoricalproblem.themagnetizinginrushcurrentcausesSuppressorisanimportantfeatureofthestrategyadoptedbymagnetizinginrushcurrentisnot"escape",but"suppression."Inrushcurrenttheoryandpracticethatcansuppressoreveneliminate,becausethesourceofinrushcurrentisgeneratedinthetransformerwindingsoneithersidefelttheappliedvoltageincreases,basedonfluxconservationtheorem,thewindingsinthemagneticcircuitwillproduceasinglepolarityofthemagneticbias,suchaspartialpoleandtransformerofexactlythesameastheoriginalremanencepolarity,itmaybiasmagneticremanenceandsteady-statefluxsuperimposedwiththeresultofmagneticsaturation,thusgreatlyreducingthemagnetizingreactanceofthetransformerwindings,andtheninducedasignificantinrushcurrentvalue.Asthepartialmagneticpolarityandthevalueisappliedvoltageswitchbyselectingthephaseanglecontrol,andtherefore,ifwecangraspthepowertransformerwhenthelastofremanentmagneticpolarity,theycandropbywhenthecontroltransformerthesupplyvoltagephaseangle,whichallowsmagneticbiaswithoppositepolarityremanence,whicheliminatetheinrushcurrentofthesoil-magneticsaturation,toachievetheinrushcurrentForalongtime,peoplefounditimpossibletomeasurethetransformerpolarityandremanencevalues,andthushadtoabandontheuseoftheideaofpartialremanencemagneticoffset.Inrushcurrentinresponsetothestrategydoesnotappearonthetwosmoothroad,aroadthroughthecontrolpowertransformervoltagedropclosingphaseangle,sothatitdoesnotproducemagneticbias,inordertoavoidmagneticsaturationoccurswhenthepowerdrops.Theotherwayistheuseofphysicalormathematicalmethodforidentifyingthecharacteristicsofmagnetizinginrushcurrent,inordertolockinthepowertransformerprotectiondevicesdrop,thattheaforementioned"avoid"strategy.Thetwofatalroadhasitsproblems,capturedoesnotproducemagneticbiasvoltageclosingangleofonlytwo,namely,thetwosinusoidalvoltagepeakpoint(90°or270°),ifyoudeviatefromthesetwopoints,partialtherewillbemagnetic,whichrequirescontroloftheclosingpartofallinstitutions(includingcircuitbreakers)shouldbeaccurate,stableoperatingtime,because,as1millisecondtimedriftaction,closingphaseangleof18°willproducetheerror.Inaddition,three-phasevoltageofthepeakisnotatthesametimecoming,butthedifferencebetween120°,tocompletelyeliminatethethree-phaseinrushcurrent,mustbetime-phasethree-phasecircuitbreakerclosingcanbeachieved,andthecurrentoperatingrulesprohibitsuchpower

willbeleadtotime-sharing-phasesplit-phaseoperationrunning,nottomentionsomecircuitbreakersinthesub-phasestructurecannotoperate.dentificationwiththephysicalandmathematicalmethodsofmagnetizinginrushcurrentratherdifficult,becausethecharacteristicsofmagnetizinginrushcurrentandalotoffactors,suchasclosingphaseangle,theelectromagneticparametersofthetransformerandsoon.Alargenumberofscholarsandengineersthroughdecadesofunremittingeffortsstillcannotfindaneffectiveway,becauseofitshighdegreeofdifficulty,thatisto"avoid"strategydifficult,theAchillesheelofthisstrategyistotoleratetheotherexcitationinrushcurrentoccurs,thepollutionofitspowergridandelectricalequipment,thereisstilldestructive.UxNauasformerdiagram2-1Figure2-1isasvoltageoftheprTrale-phasetransformerstruct UxNauasformerdiagram2-1Figure2-1isasvoltageoftheprTrale-phasetransformerstruct —口〔1一equationngmary^indi^ofTheequaur,wecanwritetheno-load竺(2.1)ul=ilRl+Nl出(2.1)WhereN1,R1,respectively,fortheprimarywindingturnsandtheresistance以毗勰+&)=腥艮i+ (2.2)(2.1)canberewrittenasWhereat=0,U1,suchasignoringtheinitialphaseangleresistorR1,which（2.3）LetR1=0,weobtainthesolution(2.3)-typeequationshaveanexpressionforthemagneticflux0中二衛(wèi)曾喝（勰+@）+C(2.4)(2.4)Basedonfluxconservationtheorem,intheclosingmomentsmagneticfluxcannot

changesuddenly,youcanfindtheintegrationconstantC.（2.5）C=^-Cosa（2.5）iiWi中=^_[Cosa-+南]*Ni u=^f^Cosa-Cas^+or)] (2.6)中=旦Theamplitudeofthetotalfluxfromequation(2.6)isnotdifficulttoseethattheappliedvoltagetransformeru1intheearlyphaseangleadifferentwhenclosingthemagneticfluxgeneratedby0isnotthesame,theequation(2.6)isrewrittenas=^mCQsa-^mCas{a^+or)_Cy?- 曰(2.7)forthetransientflux,thatis,magneticbias,intheclosingmoments0pvalueofaforthe90°or270°dropat0p=0,at0°or180°when中p=^mCosadroppeduptothepeak0m0p.Equation(2.7)in forthesteady-stateflux,asaperiodicfunction.Figure2-2forthedrop-closinganglea=0,thefluxcurve,thesteady-statefluxdiagram0s,0is0sand0ptotalfluxsynthetic(nottakingintoaccounttheremanence0res),0satforthetransformersaturationflux.Forthelosslesstransformer(R1=0)magneticbias0pwillnotdecay,thesolidlineshows,forlossytransformer(R1>0)Dashedline.AscanbeseenfromFigure2-3inthevoltagephaseanglerange01to02greaterthanthetotalflux0saturationflux0sat,magneticsaturation,resultinginrushcurrentiy,iyhasadiscontinuity.ClosingangleaClosinganglea=0,thefluxcurveofFigure2-2 c + 1 1 , 9=魂+@=汗 ，F(xiàn)orthelosslesstransformer0andiyisabout evensymmetryofthewaveform,whilethediscontinuityintheiy=0istheangularrangeof0 theevensymmetricwaveform.For0andiyisdetrimentaltothetransformerwillnolongersymmetricalrelationship.Whentakingintoaccounttheremanence,theremanencewillbethetotalmagneticflux,magneticbias(transientflux)andsteady-statefluxofthethreecomponents.DifficulttoseeinFigure2-2Biasinthecase,suchasremanenceispositive,thetotalfluxcurveupwardshift,thatmoresaturatedmagneticcircuit,inrushcurrentamplitudewillbegreater.Ifremanenceisnegative,theinrushcurrentissuppressed.CorematerialhysteresisloopinFigure2-3、Figure2-2isthehysteresisloopsofferromagneticmaterials,whichdescribestheexcitationcoilinthemagneticcircuitontheACvoltageapplied,thecorrespondingmagneticpotentialH-HctoHcfrombetweenthechangeinmagneticflux0generatedbyH(ormagneticfluxdensityB=0/S)inthecorrespondinghysteresisloopchanges.IftheHlineatsomepointsuddenlybacktozero,thenBwillthenfallintotheB-axiscorrespondstoacertainpoint,thepointcorrespondingtotheBvalueistheremanenceBr.Remanencevaluescanbeseenwiththeremovalofexcitationvoltageandpolarityofthephaseangle,andifinthefirstI,IIexcitationpoweroffquadrant(ie,H=0)thentheremanenceispositiveorzero,inIII,IVquadrantcutofftheexcitationpower,theremanenceisnegative.themagnetizinginrushcurrentsuppressionmethodTransformerenergizedduringnormalworkinghours,themainmagneticfluxintheappliedvoltagewaveformandthewaveformisbasicallythesame,thatisasinewave.Magneticfluxlagsthesupplyvoltageof90°,bymonitoringthesupplyvoltagewaveformtoachievethefluxwaveformmonitoring,thengetoffwhenthesupplyvoltagepolarityremanence.Droponthepowertransformermagneticbias0palsogeneratedasaresultofmagneticbias,thepowersupplyvoltagewhentheinitialphaseangleainI,IVquadrantbiasgeneratedwithintherangeofmagneticpolarityispositive,whiletheinitialphaseangleainII,iiiquadrantbiasgeneratedwithintherangeofmagneticpolarityisnegative.Clearly,theremanencepolarityshowsthatthemagneticpolaritybiascontrol,solongasthepowerdropandremanencemagneticpolarityoppositeside,heincurssurgesuppression.Figure3-1forthetransformerprimaryvoltageu,themainmagneticflux0,andthebiasmagneticremanence0Res0pwithsub-gatetherelationshipbetweentheangleandclosinganglecurve,andthesub-gatesupplyvoltageubeginningofthephaseanglea'withtheremanence0Rescurve.Themaintransformerinthesteadystateflux0lagthesupplyvoltageu90°,tTransformerno-loadpowergeneratedwhenthemagneticbiasmustcorrespondwiththesteadystatevoltageuatpowerpointonthecurveofsteady-statefluxpowerequal,oppositepolarity,Themaximumsteady-stateflux0uptothepeak0m,whiletheamplitudeofmagneticremanence0Resmaterialcharacteristics.Easytoseetheearlyphasecorrespondstothesameangleaorclosingthesub-gateinitialphaseanglea'andtheresultingmagneticremanenceoftheverypartial.Transformerprimaryvoltageu,themainmagneticflux0,andthebiasmagneticremanence0Res0pwithsub-gatetherelationshipbetweentheangleandclosinganglecurveoftheopposite,thatismeasuredbythesub-gatesub-gatevoltageanglea',anda'preserved,theselectionofthetransformerinthenextdropintheclosingangleaequaltoa',whencoupledwithpower,andbiasmagneticremanencecanreverse,theywillbelessthanthesynthesisofmagneticfluxsaturationflux0sat.(Duetosaturationfluxisgenerallylargerthanthesteady-statefluxpeakselection),themagneticcircuitisnotsaturated,inordertoachieveinrushcurrentsuppression.Asthethree-phasethree-phasesupplyvoltageofthecircuitbreakerwhenthelinkagehasbeencutthree-phasesub-phaseofthedifferencebetweenthegate120°,thephasedifferencebetweentheremanencepolarityis120°,andwhenclosingthethree-phasethree-phaseco-linkageinitialphaseangledifferencebetweenthegateis120°,thephasedifferencebetweenthepartialpoleisalso120°,sothatthenaturalrealizationofthethree-phasetransformermagneticcircuitbiasmagneticandremanenceareoffsettoavoidacircuitbreakermustbewithatimeshareinordertosuppressinrushcurrentdemanding,thatsupportforthree-phasethree-phasecircuitbreakerlinkagesurgesuppression.Aslongasthepartialinhibitionofinrushcurrentandremanentmagneticpolarityoppositeto,arenotrequiredtofullyoffset,sowhentheclosinganglerelativetoagreaterangleoftheprevioussub-gatebias,aslongasnomagneticbiasandremanenceareaddedtogether,themagneticcircuitnotsaturated,whichgreatlyreducestheoperatingtimeofcircuitbreakeroperatingmechanismprecisionrequirementsforthepracticalapplicationofthistechnologylaidthefoundation.Suppressorandfastcuttingofsuchdevicesandequipmentcanberealizedfromtheinvestmentunitlinkedbycoldstandbysparetransformerrun,whichwillgreatlyreduceno-loadtransformerhotstandbymodeenergyconsumption.Figure3-3presentsselectedfourinrushcurrentIyandthesub-gateanglea'andtheclosingangleaofthecurve,youcansee,intheclosingangleaof90°or270°,dropthetransformerinrushcurrentandtransformerbeforesub-sub-gateanglehasnothingtodo,becausethetransformerprimaryvoltageoverpeakpowerdoesnotproducemagneticbias,regardlessofwhethertheoriginaltransformermagneticsaturationremanencewillnot