避雷器額定電(dian)壓、工頻放(fang)電(dian)電(dian)壓、沖擊放(fang)電(dian)電(dian)壓和沖擊電(dian)流殘壓是表征避雷器電(dian)氣(qi)性(xing)能的(de)幾項(xiang)重要指標，它們(men)是根據系統的(de)參(can)數、運行方式及絕(jue)緣配合的(de)原則來(lai)確定的(de)。今天，鈞和電(dian)子(zi)就(jiu)避雷器的(de)這項(xiang)電(dian)氣(qi)性(xing)能做(zuo)如(ru)下詳細介紹：

一、額定電壓

避雷器能夠可靠地工作并能完成預期的動作負載試驗的最大允許工頻電壓，稱為避雷器的額定電壓。對于有間隙避雷器而言，我國、德國和蘇聯曾稱這一電壓為滅弧電壓，現在以IEC標準統一定義。為確保避雷器正常工作，必須使這一電壓設計得大于安裝出可能出現的最大短時工頻電壓。

為了確(que)定和(he)計算(suan)避雷器額定電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)，需要分析(xi)避雷器安裝(zhuang)處工頻電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)的變(bian)化(hua)情況。在(zai)系統中(zhong)，產(chan)生短時(shi)工頻電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)升(sheng)高(gao)(gao)的起(qi)因(yin)(yin)主要有三(san)個：一是(shi)(shi)發電(dian)(dian)(dian)機(ji)因(yin)(yin)突然甩負荷(he)后轉速加快，引起(qi)母線(xian)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)升(sheng)高(gao)(gao)；二是(shi)(shi)由于(yu)(yu)電(dian)(dian)(dian)感-電(dian)(dian)(dian)容(rong)效應，遠距離輸電(dian)(dian)(dian)線(xian)路空載時(shi)末端電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)升(sheng)高(gao)(gao)；三(san)是(shi)(shi)發生單(dan)項接(jie)(jie)地(di)故障時(shi)，健全(quan)相電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)升(sheng)高(gao)(gao)。運行經驗表明，全(quan)線(xian)跳閘、甩負荷(he)與單(dan)項接(jie)(jie)地(di)故障同(tong)時(shi)發生的機(ji)會是(shi)(shi)十(shi)分罕見的，故障往往出現于(yu)(yu)線(xian)路局(ju)部(bu)，因(yin)(yin)此，無須考慮這三(san)種(zhong)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)同(tong)時(shi)升(sheng)高(gao)(gao)的可能性(xing)。我國關于(yu)(yu)甩負荷(he)引起(qi)的母線(xian)電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)升(sheng)高(gao)(gao)的實測數據不超過1.37倍相電(dian)(dian)(dian)壓(ya)(ya)(ya)(ya)。

二、工頻放(fang)電電壓

工頻(pin)放電(dian)(dian)電(dian)(dian)壓是有(you)串(chuan)聯間(jian)隙(xi)避雷器(qi)的(de)一(yi)個(ge)重要參(can)數。工頻(pin)放電(dian)(dian)電(dian)(dian)壓具(ju)有(you)一(yi)定的(de)分(fen)散(san)性，分(fen)散(san)帶的(de)寬窄(zhai)與火花(hua)間(jian)隙(xi)的(de)結(jie)構、預(yu)照(zhao)射條件和工藝(yi)水(shui)平有(you)很(hen)大的(de)關(guan)系。按我(wo)國的(de)制造水(shui)平，在碳化硅避雷器(qi)設(she)計中，取工頻(pin)放電(dian)(dian)電(dian)(dian)壓平均(jun)值的(de)±7%～10%為(wei)其上、下限。許多產品的(de)分(fen)散(san)帶僅(jin)為(wei)±5%。

確定工頻放(fang)電電壓(ya)(ya)下限時，應考慮兩(liang)個條件，一是必須保證避雷(lei)器(qi)能夠可靠地熄弧(hu)；二(er)是對于非限制操作過(guo)電壓(ya)(ya)的(de)避雷(lei)器(qi)，其工頻放(fang)電電壓(ya)(ya)應該(gai)大于系統的(de)操作過(guo)電壓(ya)(ya)，防止在這種電壓(ya)(ya)出現時動作，損壞避雷(lei)器(qi)。

為闡明工頻放電電壓和避雷器滅弧能力之間的內在聯系，使用切斷比Kq的概念來描述閥式避雷器這一特性，它等于工頻放電電壓下限制Umin與避雷器額定電壓U_R之比。

三(san)、沖擊放電(dian)電(dian)壓和沖擊電(dian)流(liu)殘壓

沖擊(ji)放(fang)(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)和沖擊(ji)電(dian)(dian)(dian)流殘壓(ya)(ya)是供(gong)絕緣配合計算用的(de)重要數據。由氣體(ti)放(fang)(fang)電(dian)(dian)(dian)理論(lun)得知(zhi)，有(you)串聯間隙的(de)避雷(lei)器的(de)沖擊(ji)放(fang)(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)與所施電(dian)(dian)(dian)壓(ya)(ya)的(de)陡(dou)度有(you)很大關(guan)系，因此，標準規定(ding)(ding)了在(zai)(zai)1.2/50μs標準波、電(dian)(dian)(dian)壓(ya)(ya)上升速率為一定(ding)(ding)值(zhi)時，陡(dou)波頭沖擊(ji)電(dian)(dian)(dian)壓(ya)(ya)及模擬不同(tong)波頭的(de)操作(zuo)過電(dian)(dian)(dian)壓(ya)(ya)等作(zuo)用下的(de)放(fang)(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)值(zhi)。波頭越陡(dou)，放(fang)(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)越高(gao)。根據實測，同(tong)一避雷(lei)器在(zai)(zai)前述陡(dou)波頭沖擊(ji)電(dian)(dian)(dian)壓(ya)(ya)作(zuo)用時的(de)放(fang)(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)壓(ya)(ya)最大值(zhi)可達(da)標準波作(zuo)用的(de)1.15倍左右(you)。

沖擊(ji)電流殘(can)壓(ya)隨沖擊(ji)電流波(bo)形不同(tong)而不同(tong)，它是非線(xian)性(xing)電阻(zu)片(pian)呈現處的(de)固有特性(xing)。在技術條件(jian)中，通常(chang)給(gei)出的(de)是在標準放電電流幅值、7/20μs波(bo)形作(zuo)用時的(de)殘(can)壓(ya)。沖擊(ji)電流上升的(de)陡度越大，非線(xian)性(xing)電阻(zu)的(de)殘(can)壓(ya)也隨之變大。ZnO電阻(zu)片(pian)的(de)這一變化(hua)比(bi)SiC電阻(zu)片(pian)小

實際應用(yong)中，選取(qu)標(biao)準(zhun)波沖擊放電(dian)電(dian)壓(ya)和標(biao)稱(cheng)放電(dian)電(dian)流殘(can)壓(ya)中的(de)(de)(de)一個最大者(zhe)作為避(bi)雷(lei)(lei)器(qi)的(de)(de)(de)保(bao)(bao)(bao)(bao)護(hu)(hu)水(shui)平。保(bao)(bao)(bao)(bao)護(hu)(hu)水(shui)平與避(bi)雷(lei)(lei)器(qi)額(e)定電(dian)壓(ya)之比稱(cheng)為保(bao)(bao)(bao)(bao)護(hu)(hu)比，它是表(biao)征避(bi)雷(lei)(lei)器(qi)保(bao)(bao)(bao)(bao)護(hu)(hu)特性的(de)(de)(de)一個指(zhi)標(biao)，其值越低，保(bao)(bao)(bao)(bao)護(hu)(hu)性能越優(you)。