電(dian)纜(lan)(lan)故(gu)障(zhang)(zhang)(zhang)的(de)探測一般要經過診斷、測距(ju)(ju)、定點三(san)個(ge)步驟。電(dian)纜(lan)(lan)故(gu)障(zhang)(zhang)(zhang)的(de)測試(shi)一般分(fen)為兩個(ge)過程:即故(gu)障(zhang)(zhang)(zhang)電(dian)纜(lan)(lan)故(gu)障(zhang)(zhang)(zhang)點距(ju)(ju)離的(de)測試(shi)；故(gu)障(zhang)(zhang)(zhang)點定點的(de)測試(shi)。故(gu)障(zhang)(zhang)(zhang)電(dian)纜(lan)(lan)故(gu)障(zhang)(zhang)(zhang)點距(ju)(ju)離的(de)測試(shi)即測距(ju)(ju)方(fang)法有三(san)種:回路電(dian)橋平衡法；低(di)壓(ya)脈沖(chong)反射法；閃絡法。

　　回路電(dian)橋(qiao)平(ping)衡法(fa)(fa)是使(shi)用直流(liu)電(dian)橋(qiao)對電(dian)纜(lan)故障(zhang)(zhang)進行測(ce)距(ju)(ju)的一種方法(fa)(fa)，簡稱電(dian)橋(qiao)法(fa)(fa)，現場(chang)人(ren)員有把Ｒf＜100kΩ的故障(zhang)(zhang)稱為低阻故障(zhang)(zhang)的習慣，主要是因為傳統的電(dian)橋(qiao)法(fa)(fa)可(ke)以測(ce)量(liang)這類故障(zhang)(zhang)。電(dian)橋(qiao)法(fa)(fa)對于短距(ju)(ju)離電(dian)纜(lan)故障(zhang)(zhang)的測(ce)距(ju)(ju)，準(zhun)確度相當高(gao)，因此(ci)，目前還在使(shi)用。基于電(dian)纜(lan)沿線(xian)均(jun)勻(yun)，電(dian)纜(lan)長(chang)度與(yu)纜(lan)芯電(dian)阻成正比，并(bing)根據(ju)惠(hui)斯登電(dian)橋(qiao)的原理，將電(dian)纜(lan)短路接地、故障(zhang)(zhang)點(dian)兩(liang)側的環線(xian)電(dian)阻引入直流(liu)電(dian)橋(qiao)，測(ce)量(liang)其比值(zhi)(zhi)。由測(ce)得的比值(zhi)(zhi)和電(dian)纜(lan)全長(chang)，可(ke)獲(huo)得測(ce)量(liang)端(duan)到故障(zhang)(zhang)點(dian)的距(ju)(ju)離。

　　使(shi)用電(dian)(dian)(dian)(dian)(dian)橋法對(dui)(dui)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)單相接(jie)地(di)(di)故(gu)障(zhang)測(ce)距原理是先在電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)的另一(yi)(yi)端(duan)，將電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)的故(gu)障(zhang)相和正常相的電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)導(dao)體(ti)(ti)(ti)用不小于(yu)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)截面的導(dao)線跨(kua)接(jie)。然后(hou)在一(yi)(yi)端(duan)將故(gu)障(zhang)相的電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)導(dao)體(ti)(ti)(ti)接(jie)在電(dian)(dian)(dian)(dian)(dian)橋的另一(yi)(yi)端(duan)子(zi)上。使(shi)用電(dian)(dian)(dian)(dian)(dian)橋法對(dui)(dui)電(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)兩(liang)相短路或兩(liang)相短路并接(jie)地(di)(di)，故(gu)障(zhang)進行測(ce)距時，需(xu)要(yao)有一(yi)(yi)個(ge)非故(gu)障(zhang)導(dao)體(ti)(ti)(ti)和故(gu)障(zhang)導(dao)體(ti)(ti)(ti)一(yi)(yi)起形成一(yi)(yi)個(ge)環，當電(dian)(dian)(dian)(dian)(dian)橋平衡(heng)時便可得到故(gu)障(zhang)點的距離。

　　低壓脈(mo)沖(chong)(chong)反(fan)(fan)射法。低壓脈(mo)沖(chong)(chong)反(fan)(fan)射法探測電纜(lan)故(gu)(gu)障(zhang)(zhang)是由儀器(qi)的(de)脈(mo)沖(chong)(chong)發生(sheng)器(qi)發出一(yi)個脈(mo)沖(chong)(chong)波，通(tong)過(guo)引線把脈(mo)沖(chong)(chong)波送到電纜(lan)的(de)故(gu)(gu)障(zhang)(zhang)相上，脈(mo)沖(chong)(chong)波沿電纜(lan)的(de)線芯傳(chuan)播，當(dang)傳(chuan)播到故(gu)(gu)障(zhang)(zhang)點時，由于故(gu)(gu)障(zhang)(zhang)點電纜(lan)的(de)波阻發生(sheng)變(bian)化，因而有一(yi)脈(mo)沖(chong)(chong)信號被(bei)反(fan)(fan)射回(hui)來，用示波器(qi)在測試(shi)端記錄下從發送脈(mo)沖(chong)(chong)和反(fan)(fan)射脈(mo)沖(chong)(chong)之(zhi)間(jian)的(de)時間(jian)間(jian)隔，即可算(suan)出測試(shi)端距故(gu)(gu)障(zhang)(zhang)點的(de)距離(li)。

　　開路與低(di)(di)阻故(gu)(gu)障(zhang)可用低(di)(di)壓(ya)脈(mo)(mo)沖(chong)(chong)反射法(fa)，低(di)(di)壓(ya)脈(mo)(mo)沖(chong)(chong)反射法(fa)的*之處在(zai)于使現(xian)場(chang)測得的故(gu)(gu)障(zhang)波(bo)(bo)形得到大大簡(jian)化，將復雜的高(gao)壓(ya)沖(chong)(chong)擊閃(shan)絡波(bo)(bo)形變成了非(fei)常容易判(pan)(pan)讀(du)的類似于低(di)(di)壓(ya)脈(mo)(mo)沖(chong)(chong)法(fa)的短路故(gu)(gu)障(zhang)波(bo)(bo)形。降低(di)(di)了對操作人員的技術要(yao)求和經驗要(yao)求，提高(gao)了現(xian)場(chang)故(gu)(gu)障(zhang)的判(pan)(pan)斷準確(que)率，達(da)到快(kuai)速準確(que)測試電纜故(gu)(gu)障(zhang)的目(mu)的。

　　閃(shan)(shan)絡(luo)(luo)法(fa)。閃(shan)(shan)絡(luo)(luo)法(fa)的(de)基(ji)本原理(li)與(yu)低(di)壓脈(mo)沖(chong)法(fa)相似，是利用電(dian)(dian)波在電(dian)(dian)纜(lan)(lan)內傳(chuan)播時在故(gu)障(zhang)點(dian)產生反射的(de)原理(li)，記下電(dian)(dian)波在故(gu)障(zhang)電(dian)(dian)纜(lan)(lan)測(ce)試端的(de)故(gu)障(zhang)點(dian)之間往返一次的(de)時間，再(zai)根據(ju)波速來計算電(dian)(dian)纜(lan)(lan)故(gu)障(zhang)點(dian)位置。據(ju)統計，高(gao)阻(zu)及閃(shan)(shan)絡(luo)(luo)性(xing)故(gu)障(zhang)約占整個電(dian)(dian)纜(lan)(lan)故(gu)障(zhang)總數的(de)90%。高(gao)阻(zu)故(gu)障(zhang)要用沖(chong)擊(ji)閃(shan)(shan)絡(luo)(luo)法(fa)，而閃(shan)(shan)絡(luo)(luo)性(xing)故(gu)障(zhang)可用直流閃(shan)(shan)絡(luo)(luo)法(fa)測(ce)試。實際現(xian)場上是通(tong)過(guo)試驗方法(fa)區分(fen)高(gao)阻(zu)與(yu)閃(shan)(shan)絡(luo)(luo)性(xing)故(gu)障(zhang)的(de)。