變壓器是電網變換電壓和傳送電能的電氣設備，是電網向用戶供電的載體，變壓器的a全可靠運行情系萬家燈火。然而在電網運行中由于諸多原因會產生過電壓，而變壓器的絕緣水平相對比較薄弱，在變壓器損壞的原因中，過電壓造成損壞的概率Z大。在電網運行中因某種原因產生過電壓，必將導致變壓器的損壞，其絕緣水平主要由雷電擊耐受電壓和工頻耐受電壓來決定。

　　過電(dian)壓(ya)(ya)系指對絕(jue)緣有危(wei)險的(de)突(tu)然電(dian)壓(ya)(ya)升(sheng)高(gao)，這(zhe)種非正常的(de)電(dian)壓(ya)(ya)升(sheng)高(gao)，其幅值(zhi)可達設備額定電(dian)壓(ya)(ya)的(de)幾倍以上，嚴重威(wei)脅(xie)變(bian)壓(ya)(ya)器(qi)(qi)絕(jue)緣的(de)a全(quan)，若過電(dian)壓(ya)(ya)持續(xu)時(shi)間較長，必將造成變(bian)壓(ya)(ya)器(qi)(qi)的(de)損(sun)壞。為確(que)保電(dian)網(wang)運行(xing)中(zhong)變(bian)壓(ya)(ya)器(qi)(qi)的(de)a全(quan)，除選用變(bian)壓(ya)(ya)器(qi)(qi)外(wai)，還要對變(bian)壓(ya)(ya)器(qi)(qi)設置合理的(de)過電(dian)壓(ya)(ya)保護措(cuo)施。

　　一、電(dian)(dian)網過電(dian)(dian)壓產生的機理

　　電(dian)(dian)(dian)(dian)力系統(tong)的(de)(de)(de)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓一(yi)般(ban)可分(fen)為暫時(shi)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓(工頻過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓、諧(xie)振過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓、弧光接地(di)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓)、操(cao)(cao)作過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓、雷(lei)電(dian)(dian)(dian)(dian)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓等(deng)。暫時(shi)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓主(zhu)要(yao)由單相(xiang)接地(di)故(gu)(gu)障(zhang)(zhang)、諧(xie)振等(deng)引(yin)起(qi)的(de)(de)(de)。諧(xie)振過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓是(shi)電(dian)(dian)(dian)(dian)網中(zhong)電(dian)(dian)(dian)(dian)氣設備發生故(gu)(gu)障(zhang)(zhang)，或頻繁操(cao)(cao)作設備引(yin)起(qi)電(dian)(dian)(dian)(dian)網中(zhong)電(dian)(dian)(dian)(dian)感和電(dian)(dian)(dian)(dian)容匹配(pei)而構成(cheng)諧(xie)振回路，在(zai)條件 下(xia)產(chan)生電(dian)(dian)(dian)(dian)能(neng)、磁能(neng)轉換而引(yin)起(qi)的(de)(de)(de)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓，如是(shi)變壓器的(de)(de)(de)勵磁電(dian)(dian)(dian)(dian)感和對地(di)電(dian)(dian)(dian)(dian)容產(chan)生的(de)(de)(de)鐵磁諧(xie)振，其引(yin)起(qi)的(de)(de)(de)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓會更高。弧光接地(di)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓系因(yin)(yin)系統(tong)發生單相(xiang)接地(di)故(gu)(gu)障(zhang)(zhang)，在(zai)接地(di)點因(yin)(yin)弧光放(fang)電(dian)(dian)(dian)(dian)而引(yin)起(qi)的(de)(de)(de)過(guo)(guo)(guo)電(dian)(dian)(dian)(dian)壓。

　　操作過電(dian)壓系因電(dian)網(wang)狀態的突變而引(yin)起電(dian)磁場 的急劇變化，或投切大(da)容量設(she)備，或是(shi)對(dui)設(she)備的操作失(shi)誤等而引(yin)起 快速釋(shi)放時(shi)產生的過電(dian)壓。主(zhu)要表現在空載(zai)線路、變壓器的開斷和重合閘等。

　　雷電(dian)過(guo)(guo)電(dian)壓(ya)是大氣中帶(dai)有大量正電(dian)荷雷云與帶(dai)負(fu)電(dian)荷雷云相遇時，發(fa)生雷云放(fang)電(dian)而引起(qi)的(de)過(guo)(guo)電(dian)壓(ya)。雷電(dian)過(guo)(guo)電(dian)壓(ya)可分為直(zhi)擊雷過(guo)(guo)電(dian)壓(ya)和(he)感應過(guo)(guo)電(dian)壓(ya)。直(zhi)接(jie)雷過(guo)(guo)電(dian)壓(ya)是雷云直(zhi)接(jie)對設(she)備、構(gou)件等導體的(de)放(fang)電(dian)產(chan)生的(de)，而感應過(guo)(guo)電(dian)壓(ya)則是電(dian)磁場的(de)急劇(ju)變化而產(chan)生的(de)。

　　二、電網過電壓(ya)對變壓(ya)器的危害(hai)

　　電(dian)(dian)網中產生(sheng)(sheng)的(de)幾(ji)種(zhong)過電(dian)(dian)壓(ya)(ya)(ya)，真正對變壓(ya)(ya)(ya)器(qi)絕緣(yuan)和保護裝(zhuang)置(zhi)產生(sheng)(sheng)影響的(de)，主要取決(jue)于過電(dian)(dian)壓(ya)(ya)(ya)的(de)波(bo)(bo)形。幅值和持(chi)續(xu)時間。考核(he)設(she)備絕緣(yuan)水平的(de)電(dian)(dian)壓(ya)(ya)(ya)波(bo)(bo)形有三種(zhong)：短波(bo)(bo)前的(de)雷電(dian)(dian)波(bo)(bo)、長波(bo)(bo)前的(de)操作波(bo)(bo)和低頻電(dian)(dian)壓(ya)(ya)(ya)波(bo)(bo)。設(she)備絕緣(yuan)對雷電(dian)(dian)、操作或工(gong)頻電(dian)(dian)壓(ya)(ya)(ya)的(de)耐受能力應由相應的(de)波(bo)(bo)形電(dian)(dian)壓(ya)(ya)(ya)來(lai)檢(jian)驗(yan)。

　　在(zai)(zai)(zai)過電(dian)(dian)壓(ya)(ya)(ya)對(dui)變(bian)(bian)壓(ya)(ya)(ya)器(qi)(qi)(qi)造(zao)成(cheng)(cheng)損壞的(de)事故中，雷電(dian)(dian)過電(dian)(dian)壓(ya)(ya)(ya)導致絕(jue)緣(yuan)擊穿損壞的(de)機率Z多。當電(dian)(dian)網(wang)遭受雷擊時(shi)，在(zai)(zai)(zai)線(xian)路(lu)導線(xian)上(shang)會(hui)產生一種振幅很大，作用(yong)(yong)時(shi)間很短的(de)非周(zhou)期性(xing)脈沖(chong)電(dian)(dian)壓(ya)(ya)(ya)波，它以(yi)光速(su)沿線(xian)傳輸，先在(zai)(zai)(zai)線(xian)路(lu)避(bi)(bi)雷器(qi)(qi)(qi)放電(dian)(dian)，余波經變(bian)(bian)壓(ya)(ya)(ya)器(qi)(qi)(qi)入(ru)地(di)，當余波經變(bian)(bian)壓(ya)(ya)(ya)器(qi)(qi)(qi)保護的(de)避(bi)(bi)雷器(qi)(qi)(qi)時(shi)，將(jiang)產生電(dian)(dian)壓(ya)(ya)(ya)降(殘(can)壓(ya)(ya)(ya))而(er)(er)作用(yong)(yong)在(zai)(zai)(zai)變(bian)(bian)壓(ya)(ya)(ya)器(qi)(qi)(qi)上(shang)。假如變(bian)(bian)壓(ya)(ya)(ya)器(qi)(qi)(qi)與避(bi)(bi)雷器(qi)(qi)(qi)之間存(cun)在(zai)(zai)(zai)電(dian)(dian)氣距(ju)離，殘(can)壓(ya)(ya)(ya)在(zai)(zai)(zai)進(jin)入(ru)前(qian)會(hui)在(zai)(zai)(zai)這段距(ju)離的(de)導線(xian)振蕩而(er)(er)導致電(dian)(dian)壓(ya)(ya)(ya)的(de)升(sheng)高，造(zao)成(cheng)(cheng)加(jia)在(zai)(zai)(zai)變(bian)(bian)壓(ya)(ya)(ya)器(qi)(qi)(qi)上(shang)電(dian)(dian)壓(ya)(ya)(ya)高于殘(can)壓(ya)(ya)(ya)，從而(er)(er)對(dui)變(bian)(bian)壓(ya)(ya)(ya)器(qi)(qi)(qi)絕(jue)緣(yuan)a全造(zao)成(cheng)(cheng)威脅。所以(yi)在(zai)(zai)(zai)安(an)裝變(bian)(bian)壓(ya)(ya)(ya)器(qi)(qi)(qi)的(de)保護避(bi)(bi)雷器(qi)(qi)(qi)時(shi)，應盡(jin)量實現避(bi)(bi)雷器(qi)(qi)(qi)和(he)變(bian)(bian)壓(ya)(ya)(ya)器(qi)(qi)(qi)保持零(ling)·距(ju)離。

　　電網內出(chu)現(xian)的諧振過(guo)電壓(ya)(ya)或操作過(guo)電壓(ya)(ya)，其過(guo)電壓(ya)(ya)幅值也(ye)高，持(chi)續時(shi)間(jian)也(ye)較長。同樣也(ye)會威脅到(dao)變(bian)壓(ya)(ya)器運行的a全，甚至還會導(dao)致絕緣擊穿而毀壞變(bian)壓(ya)(ya)器。

　　此(ci)外(wai)，逆(ni)變(bian)換過電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)對(dui)變(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)的(de)(de)危害也(ye)(ye)不(bu)容(rong)忽視。當變(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)采(cai)(cai)用(yong)避雷(lei)器(qi)(qi)進行(xing)防雷(lei)保護時，其(qi)避雷(lei)器(qi)(qi)接(jie)地線(xian)、變(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)中(zhong)(zhong)性(xing)(xing)線(xian)和變(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)外(wai)殼采(cai)(cai)用(yong)"三位一(yi)體(ti)"的(de)(de)方式(shi)接(jie)地。變(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)運行(xing)中(zhong)(zhong)若高壓(ya)(ya)(ya)(ya)(ya)(ya)側遭受雷(lei)擊(ji)(ji)時，會(hui)引起避雷(lei)器(qi)(qi)放(fang)電(dian)(dian)(dian)(dian)，產(chan)(chan)生(sheng)的(de)(de)殘(can)壓(ya)(ya)(ya)(ya)(ya)(ya)作(zuo)用(yong)在高壓(ya)(ya)(ya)(ya)(ya)(ya)繞(rao)(rao)組上。由于高壓(ya)(ya)(ya)(ya)(ya)(ya)繞(rao)(rao)組阻抗很大(da)(da)，容(rong)抗很小，雷(lei)電(dian)(dian)(dian)(dian)流只在高壓(ya)(ya)(ya)(ya)(ya)(ya)繞(rao)(rao)組和對(dui)地電(dian)(dian)(dian)(dian)容(rong)上·流過，其(qi)電(dian)(dian)(dian)(dian)路經(jing)接(jie)地點(dian)放(fang)電(dian)(dian)(dian)(dian)時，會(hui)在接(jie)地電(dian)(dian)(dian)(dian)阻上產(chan)(chan)生(sheng)一(yi)個很大(da)(da)的(de)(de)沖(chong)擊(ji)(ji)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)降，此(ci)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)經(jing)過中(zhong)(zhong)性(xing)(xing)線(xian)也(ye)(ye)會(hui)施加低(di)壓(ya)(ya)(ya)(ya)(ya)(ya)繞(rao)(rao)組上，而(er)低(di)壓(ya)(ya)(ya)(ya)(ya)(ya)繞(rao)(rao)組流過雷(lei)電(dian)(dian)(dian)(dian)流也(ye)(ye)會(hui)產(chan)(chan)生(sheng)磁(ci)通。根(gen)據電(dian)(dian)(dian)(dian)磁(ci)感(gan)應(ying)原理，此(ci)磁(ci)通會(hui)在高壓(ya)(ya)(ya)(ya)(ya)(ya)繞(rao)(rao)組上按變(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)變(bian)化產(chan)(chan)生(sheng)很高感(gan)應(ying)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)，此(ci)電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)稱之(zhi)為"逆(ni)變(bian)換過電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)"。該電(dian)(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)(ya)(ya)幅值要比(bi)殘(can)壓(ya)(ya)(ya)(ya)(ya)(ya)大(da)(da)幾倍(bei)到幾十倍(bei)，同樣也(ye)(ye)會(hui)造(zao)成變(bian)壓(ya)(ya)(ya)(ya)(ya)(ya)器(qi)(qi)絕緣(yuan)的(de)(de)擊(ji)(ji)穿(chuan)而(er)損(sun)壞(huai)。

　　三(san)、電網過電壓的保(bao)護措施

　　1.裝設避(bi)雷(lei)針保護

　　避(bi)(bi)(bi)雷針能將雷電(dian)(dian)流引向自身而(er)a全入地，是保(bao)(bao)護(hu)直(zhi)擊雷的措施。變電(dian)(dian)所及(ji)電(dian)(dian)氣設(she)(she)備一(yi)般采用(yong)避(bi)(bi)(bi)雷針進行保(bao)(bao)護(hu)，其(qi)保(bao)(bao)護(hu)范(fan)圍(wei)取決于避(bi)(bi)(bi)雷針高度(du)與(yu)根數，若采用(yong)多根避(bi)(bi)(bi)雷針保(bao)(bao)護(hu)，其(qi)范(fan)圍(wei)更大效果(guo)好(hao)(hao)。同時，為避(bi)(bi)(bi)免反(fan)擊事故，避(bi)(bi)(bi)雷針的接(jie)地網(wang)設(she)(she)置與(yu)接(jie)地電(dian)(dian)阻值要符合技(ji)術規范(fan)，并使之與(yu)構架、變壓(ya)器、斷路器等設(she)(she)備之間距離滿足技(ji)術要求，才能取得(de)良好(hao)(hao)的防雷保(bao)(bao)護(hu)效果(guo)。

　　2.架設避(bi)雷(lei)線進行保(bao)護(hu)

　　在變(bian)(bian)(bian)(bian)電(dian)(dian)(dian)所近區電(dian)(dian)(dian)源進(jin)線(xian)(xian)上(shang)(shang)(shang)方架(jia)設避(bi)(bi)雷(lei)(lei)線(xian)(xian)保護(hu)，可使(shi)(shi)(shi)電(dian)(dian)(dian)源進(jin)線(xian)(xian)遭受(shou)雷(lei)(lei)電(dian)(dian)(dian)侵入波(bo)的(de)(de)(de)(de)概率大大減少。若(ruo)在避(bi)(bi)雷(lei)(lei)線(xian)(xian)以外(wai)線(xian)(xian)路上(shang)(shang)(shang)落(luo)雷(lei)(lei)時，由于進(jin)線(xian)(xian)段導線(xian)(xian)本身阻抗作用(yong)，使(shi)(shi)(shi)流過避(bi)(bi)雷(lei)(lei)器(qi)的(de)(de)(de)(de)雷(lei)(lei)電(dian)(dian)(dian)流受(shou)到限制，又(you)由于導線(xian)(xian)上(shang)(shang)(shang)的(de)(de)(de)(de)沖擊電(dian)(dian)(dian)暈(yun)的(de)(de)(de)(de)影響(xiang)，使(shi)(shi)(shi)雷(lei)(lei)電(dian)(dian)(dian)侵入波(bo)的(de)(de)(de)(de)陡(dou)度和幅(fu)值下降，從(cong)而(er)使(shi)(shi)(shi)保護(hu)變(bian)(bian)(bian)(bian)壓器(qi)的(de)(de)(de)(de)避(bi)(bi)雷(lei)(lei)器(qi)動作殘壓降低(di)，有利于與變(bian)(bian)(bian)(bian)壓器(qi)絕緣的(de)(de)(de)(de)配合，因(yin)而(er)對(dui)變(bian)(bian)(bian)(bian)壓器(qi)的(de)(de)(de)(de)防雷(lei)(lei)起(qi)到起(qi)良(liang)好作用(yong)。

　　3.裝(zhuang)設避雷(lei)器進行保(bao)護

　　電(dian)(dian)網保護(hu)過(guo)電(dian)(dian)壓(ya)(ya)(ya)(ya)的(de)(de)(de)(de)(de)避(bi)(bi)雷(lei)(lei)器(qi)，無論(lun)是無間(jian)隙的(de)(de)(de)(de)(de)氧化鋅避(bi)(bi)雷(lei)(lei)器(qi)，還是有(you)間(jian)隙的(de)(de)(de)(de)(de)普通閥式避(bi)(bi)雷(lei)(lei)器(qi)，器(qi)選擇使(shi)(shi)用的(de)(de)(de)(de)(de)一(yi)(yi)個共同(tong)原(yuan)則(ze)是：避(bi)(bi)雷(lei)(lei)器(qi)的(de)(de)(de)(de)(de)額(e)(e)定電(dian)(dian)壓(ya)(ya)(ya)(ya)應不(bu)低于避(bi)(bi)雷(lei)(lei)器(qi)安裝地點(dian)的(de)(de)(de)(de)(de)暫時過(guo)電(dian)(dian)壓(ya)(ya)(ya)(ya);變壓(ya)(ya)(ya)(ya)器(qi)中性點(dian)避(bi)(bi)雷(lei)(lei)器(qi)的(de)(de)(de)(de)(de)額(e)(e)定電(dian)(dian)壓(ya)(ya)(ya)(ya)應不(bu)低于變壓(ya)(ya)(ya)(ya)器(qi)的(de)(de)(de)(de)(de)Z高相(xiang)電(dian)(dian)壓(ya)(ya)(ya)(ya)。若避(bi)(bi)雷(lei)(lei)器(qi)的(de)(de)(de)(de)(de)額(e)(e)定電(dian)(dian)壓(ya)(ya)(ya)(ya)選低了，對閥式避(bi)(bi)雷(lei)(lei)器(qi)而(er)(er)言，若線(xian)路發生單相(xiang)接地故障時，由于變壓(ya)(ya)(ya)(ya)中性點(dian)出現過(guo)電(dian)(dian)壓(ya)(ya)(ya)(ya)而(er)(er)無法(fa)滅弧造(zao)成爆(bao)炸(zha);對無間(jian)隙氧化鋅避(bi)(bi)雷(lei)(lei)器(qi)，同(tong)樣將(jiang)使(shi)(shi)其(qi)在一(yi)(yi)次過(guo)電(dian)(dian)壓(ya)(ya)(ya)(ya)下吸收 過(guo)多而(er)(er)劣(lie)化損壞。反之，若避(bi)(bi)雷(lei)(lei)器(qi)額(e)(e)定電(dian)(dian)壓(ya)(ya)(ya)(ya)選擇高了，則(ze)相(xiang)應的(de)(de)(de)(de)(de)沖擊放電(dian)(dian)電(dian)(dian)壓(ya)(ya)(ya)(ya)和殘(can)壓(ya)(ya)(ya)(ya)將(jiang) ，保護(hu)電(dian)(dian)氣設(she)備的(de)(de)(de)(de)(de)限壓(ya)(ya)(ya)(ya)效果將(jiang)變得不(bu)好。

　　對于有(you)間(jian)隙的(de)(de)普(pu)通閥(fa)式避雷器，其(qi)閥(fa)片的(de)(de)阻(zu)值是隨通過(guo)的(de)(de)電(dian)(dian)(dian)流而(er)變化(hua)的(de)(de)，當很大(da)雷電(dian)(dian)(dian)流通過(guo)閥(fa)片時(shi)(shi)，其(qi)非線(xian)性電(dian)(dian)(dian)阻(zu)呈現很大(da)電(dian)(dian)(dian)導(dao)率，使(shi)避雷器殘壓(ya)不高。在正(zheng)常電(dian)(dian)(dian)壓(ya)時(shi)(shi)非線(xian)性電(dian)(dian)(dian)阻(zu)的(de)(de)電(dian)(dian)(dian)導(dao)率將下降，把工頻(pin)續(xu)流限制到很小的(de)(de)數(shu)值，為火花(hua)間(jian)隙切斷續(xu)流創造(zao)了(le)良好(hao)條件，使(shi)避雷器短(duan)時(shi)(shi)間(jian)作(zuo)用的(de)(de)沖擊放電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)減小，從而(er)保(bao)護了(le)變壓(ya)器的(de)(de)a全運行。

　　在變壓(ya)器防雷(lei)保護中采(cai)用了"三位一(yi)體"的(de)(de)接地方(fang)式(shi)，其(qi)接地裝置及接地電(dian)阻(zu)值能否滿足(zu)技術要求，避雷(lei)器與變壓(ya)器之(zhi)間電(dian)氣(qi)距離(li)能否實現"零(ling)·距離(li)"，這是(shi)變壓(ya)器能否得保護的(de)(de)關鍵。因變壓(ya)器遭受(shou)雷(lei)擊時，雷(lei)電(dian)流經接地電(dian)阻(zu)也(ye)(ye)會(hui)產生電(dian)壓(ya)降(jiang)，此電(dian)壓(ya)與殘壓(ya)疊加后一(yi)起作用在變壓(ya)器繞組(zu)上，同樣(yang)也(ye)(ye)會(hui)威脅到變壓(ya)器的(de)(de)a全。

　　總之，避(bi)(bi)(bi)雷(lei)(lei)器(qi)(qi)(qi)的(de)防雷(lei)(lei)效果，取決(jue)于避(bi)(bi)(bi)雷(lei)(lei)器(qi)(qi)(qi)的(de)殘壓(ya)(ya)(ya)、侵入波陡度及避(bi)(bi)(bi)雷(lei)(lei)器(qi)(qi)(qi)與變壓(ya)(ya)(ya)器(qi)(qi)(qi)之間電氣距離。在(zai)避(bi)(bi)(bi)雷(lei)(lei)器(qi)(qi)(qi)的(de)選擇上，須使其伏(fu)秒特性上限(xian)低于變壓(ya)(ya)(ya)器(qi)(qi)(qi)伏(fu)秒特性下限(xian)，避(bi)(bi)(bi)雷(lei)(lei)器(qi)(qi)(qi)殘壓(ya)(ya)(ya)也應(ying)小(xiao)于變壓(ya)(ya)(ya)器(qi)(qi)(qi)絕緣(yuan)耐壓(ya)(ya)(ya)允許程度，其數值也應(ying)小(xiao)于沖擊(ji)波的(de)幅值，這樣的(de)避(bi)(bi)(bi)雷(lei)(lei)器(qi)(qi)(qi)才會有保護(hu)過電壓(ya)(ya)(ya)的(de)效果。

　　4.變壓(ya)(ya)器(qi)中(zhong)性點過電(dian)壓(ya)(ya)的保(bao)護

　　變(bian)電(dian)(dian)所處(chu)于多(duo)雷區又是(shi)單(dan)電(dian)(dian)源進線，其三(san)相雷電(dian)(dian)侵入波機率(lv)較多(duo)，故主變(bian)壓(ya)(ya)(ya)器中性(xing)點(dian)需裝(zhuang)設避雷器保(bao)(bao)(bao)護(hu)(hu)。變(bian)壓(ya)(ya)(ya)器中性(xing)點(dian)過電(dian)(dian)壓(ya)(ya)(ya)保(bao)(bao)(bao)護(hu)(hu)的(de)設置(zhi)，可單(dan)獨(du)采用(yong)(yong)專門保(bao)(bao)(bao)護(hu)(hu)變(bian)壓(ya)(ya)(ya)器中性(xing)點(dian)的(de)設置(zhi)，可單(dan)獨(du)采用(yong)(yong)專門保(bao)(bao)(bao)護(hu)(hu)變(bian)壓(ya)(ya)(ya)器中性(xing)點(dian)的(de)無間隙氧化(hua)鋅避雷器(簡稱中性(xing)點(dian)MOA)。采用(yong)(yong)中性(xing)點(dian)MOA，可保(bao)(bao)(bao)護(hu)(hu)雷電(dian)(dian)過電(dian)(dian)壓(ya)(ya)(ya)及操作過電(dian)(dian)壓(ya)(ya)(ya)。其優點(dian)是(shi)：動(dong)作靈(ling)敏、殘(can)壓(ya)(ya)(ya)低、通流(liu)容量大，對(dui)保(bao)(bao)(bao)護(hu)(hu)主變(bian)壓(ya)(ya)(ya)器中性(xing)點(dian)免(mian)遭過電(dian)(dian)壓(ya)(ya)(ya)具有良好效果(guo)。

　　此(ci)外，現今的中性(xing)點MOA的額定電(dian)壓較高，當中性(xing)點電(dian)位偏離不大時(shi)，MOA仍有較好的保護效果。若接地系統(tong)發生(sheng)單(dan)相(xiang)接地故障時(shi)，主變(bian)壓器中性(xing)點將產生(sheng)一倍的工頻相(xiang)電(dian)壓，此(ci)電(dian)壓也不會對MOA造成損(sun)壞(huai)。

　　若中(zhong)性(xing)點(dian)(dian)電(dian)位嚴重偏離(li)時(shi)，避(bi)(bi)雷(lei)器(qi)運行(xing)中(zhong)自(zi)身a全將受到威脅，當中(zhong)性(xing)點(dian)(dian)過電(dian)壓(ya)(ya)達到工(gong)頻相電(dian)壓(ya)(ya)的(de)(de)(de)2倍(bei)以上(shang)時(shi)，此(ci)時(shi)避(bi)(bi)雷(lei)器(qi)會因(yin)通流量不夠而(er)損壞，并可(ke)能危及(ji)主(zhu)變的(de)(de)(de)a全。盡管這種(zhong)情況發生的(de)(de)(de)概(gai)率很(hen)少，但為了主(zhu)變的(de)(de)(de)a全，除采用(yong)中(zhong)性(xing)點(dian)(dian)MOA保(bao)護(hu)主(zhu)變中(zhong)性(xing)點(dian)(dian)過電(dian)壓(ya)(ya)外，還可(ke)在避(bi)(bi)雷(lei)器(qi)邊上(shang)并聯水(shui)平棒間隙(xi)(xi)來限(xian)制(zhi)工(gong)頻過電(dian)壓(ya)(ya)。棒間隙(xi)(xi)并聯避(bi)(bi)雷(lei)器(qi)的(de)(de)(de)保(bao)護(hu)作用(yong)是：雷(lei)電(dian)、操作過電(dian)壓(ya)(ya)由避(bi)(bi)雷(lei)器(qi)承擔保(bao)護(hu)，而(er)間隙(xi)(xi)則(ze)是用(yong)來限(xian)制(zhi)避(bi)(bi)雷(lei)器(qi)上(shang)出現的(de)(de)(de)幅值較高的(de)(de)(de)工(gong)頻過電(dian)壓(ya)(ya)。這種(zhong)保(bao)護(hu)的(de)(de)(de)設(she)置方式，既對變壓(ya)(ya)器(qi)中(zhong)性(xing)點(dian)(dian)過電(dian)壓(ya)(ya)進行(xing)保(bao)護(hu)，又達到了互為保(bao)護(hu)的(de)(de)(de)目的(de)(de)(de)。

　　5.三繞組變(bian)壓器的保護

　　三(san)繞(rao)組(zu)變壓(ya)(ya)器(qi)具有高(gao)、中、低(di)壓(ya)(ya)三(san)個(ge)繞(rao)組(zu)，其(qi)(qi)運行(xing)中若遭雷擊高(gao)壓(ya)(ya)側有雷電(dian)(dian)波侵入時，會通過(guo)靜電(dian)(dian)耦合和電(dian)(dian)磁感應(ying)向(xiang)低(di)壓(ya)(ya)繞(rao)組(zu)傳遞過(guo)電(dian)(dian)壓(ya)(ya)。在高(gao)、中壓(ya)(ya)繞(rao)組(zu)運行(xing)，低(di)壓(ya)(ya)繞(rao)組(zu)開路時，低(di)壓(ya)(ya)繞(rao)組(zu)對(dui)地電(dian)(dian)容值(zhi)較小，其(qi)(qi)繞(rao)組(zu)上的(de)靜電(dian)(dian)感應(ying)電(dian)(dian)壓(ya)(ya)分(fen)量(liang)可達到較高(gao)值(zhi)，因而會危及(ji)低(di)壓(ya)(ya)繞(rao)組(zu)的(de)絕(jue)緣a全，為限制過(guo)電(dian)(dian)壓(ya)(ya)的(de)危害，低(di)壓(ya)(ya)繞(rao)組(zu)則需在出口(kou)外裝(zhuang)設避雷器(qi)進行(xing)保(bao)護。

　　變壓(ya)(ya)(ya)(ya)器(qi)(qi)運行(xing)中，若系統發生不(bu)對稱(cheng)接(jie)地故障，或(huo)斷路器(qi)(qi)的(de)非全(quan)相動作(zuo)等(deng)而出現零序電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)時，此(ci)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)將通(tong)(tong)過電(dian)(dian)(dian)容(rong)(rong)耦合傳遞到低(di)壓(ya)(ya)(ya)(ya)繞組(zu)(zu)。由于(yu)這(zhe)種電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)具有(you)工頻(pin)過電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)特性(xing)，同(tong)樣也會危及(ji)低(di)壓(ya)(ya)(ya)(ya)繞組(zu)(zu)絕緣的(de)a全(quan)。為(wei)此(ci)，除選用同(tong)期(qi)性(xing)能好的(de)斷路器(qi)(qi)外，通(tong)(tong)常在變壓(ya)(ya)(ya)(ya)器(qi)(qi)低(di)壓(ya)(ya)(ya)(ya)側母線(xian)橋上(shang)加裝(zhuang)3只Y。接(jie)線(xian)的(de)電(dian)(dian)(dian)容(rong)(rong)器(qi)(qi)，用以增加低(di)壓(ya)(ya)(ya)(ya)側對地電(dian)(dian)(dian)容(rong)(rong)，能吸收和(he)降低(di)過電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)幅值和(he)陡度，從而起到保(bao)護過電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)的(de)效果。

　　6.變(bian)壓(ya)器(qi)低壓(ya)系統的保(bao)護

　　變(bian)壓(ya)(ya)(ya)(ya)器(qi)低(di)壓(ya)(ya)(ya)(ya)側供電線(xian)路(lu)較(jiao)長，容易(yi)遭受(shou)雷電波的侵(qin)襲，當低(di)壓(ya)(ya)(ya)(ya)線(xian)路(lu)遭受(shou)雷擊時，電壓(ya)(ya)(ya)(ya)分別在(zai)低(di)壓(ya)(ya)(ya)(ya)繞(rao)組(zu)和接地(di)電阻上(shang)，侵(qin)入的雷電流(liu)由于(yu)電磁(ci)感(gan)應會按變(bian)壓(ya)(ya)(ya)(ya)器(qi)的變(bian)比(bi)在(zai)高壓(ya)(ya)(ya)(ya)繞(rao)組(zu)上(shang)產(chan)生感(gan)應過電壓(ya)(ya)(ya)(ya)。為避免逆變(bian)換過電壓(ya)(ya)(ya)(ya)對高壓(ya)(ya)(ya)(ya)繞(rao)組(zu)造成危害，其低(di)壓(ya)(ya)(ya)(ya)側出口也需裝(zhuang)設一組(zu)金屬氧化物避雷器(qi)，用以(yi)低(di)壓(ya)(ya)(ya)(ya)繞(rao)組(zu)產(chan)生的沖擊磁(ci)通，從而起到(dao)過電壓(ya)(ya)(ya)(ya)的保護作用。

　　此外，由于Y、Zn11聯結組(zu)變(bian)壓器繞組(zu)結構(gou)上的特點，若采用這種變(bian)壓器對(dui)逆變(bian)換(huan)(huan)過電(dian)氣也有很好作用，能保護"逆變(bian)換(huan)(huan)過電(dian)壓"對(dui)變(bian)壓器的損(sun)壞。

　　變(bian)壓(ya)器是電(dian)(dian)(dian)力(li)系統重要(yao)設(she)備(bei)，其絕緣水平相對比較(jiao)薄弱，而過(guo)電(dian)(dian)(dian)壓(ya)造(zao)成變(bian)壓(ya)器損壞的概率(lv)Z大。為確(que)(que)保(bao)變(bian)壓(ya)器a全可(ke)靠運行，除選(xuan)用變(bian)壓(ya)器外(wai)，仍需對運行的變(bian)壓(ya)器設(she)置過(guo)電(dian)(dian)(dian)壓(ya)保(bao)護。根據電(dian)(dian)(dian)網運行特點和接(jie)地(di)方式，變(bian)壓(ya)器中性點出現過(guo)電(dian)(dian)(dian)壓(ya)機率(lv)也較(jiao)多，除在變(bian)電(dian)(dian)(dian)所、電(dian)(dian)(dian)網進行過(guo)電(dian)(dian)(dian)壓(ya)保(bao)護外(wai)，還要(yao)在變(bian)壓(ya)器中性點設(she)置合理的過(guo)電(dian)(dian)(dian)壓(ya)保(bao)護，確(que)(que)保(bao)變(bian)壓(ya)器a全穩定運行。