電纜故障點的四種實用測定方法
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來源：金環宇電線電纜發(fa)布(bu)日(ri)期：2020-04-09 11:12
一、 電纜(lan)(lan)(lan)故(gu)障的(de)種類與(yu)判斷(duan)(duan)無(wu)論是高(gao)壓(ya)電纜(lan)(lan)(lan)或(huo)(huo)低壓(ya)電纜(lan)(lan)(lan)，在施工(gong)安裝、運行(xing)過(guo)程中經常(chang)因短路、過(guo)負荷運行(xing)、絕緣老(lao)化(hua)或(huo)(huo)外(wai)力損壞(huai)等(deng)原(yuan)因造(zao)成故(gu)障。電纜(lan)(lan)(lan)故(gu)障分為接(jie)地(di)、短路、斷(duan)(duan)線三類。三芯(xin)電纜(lan)(lan)(lan)故(gu)障類型主要有以(yi)下幾方面：一芯(xin)或(huo)(huo)兩芯(xin)接(jie)觸;二(er)相(xiang)(xiang)芯(xin)線間(jian)短路;三相(xiang)(xiang)芯(xin)線完全短路;一相(xiang)(xiang)芯(xin)線斷(duan)(duan)線或(huo)(huo)多相(xiang)(xiang)斷(duan)(duan)線。對于直接(jie)短路或(huo)(huo)斷(duan)(duan)線故(gu)障用(yong)(yong)萬(wan)用(yong)(yong)表可(ke)直接(jie)測(ce)量判斷(duan)(duan)，對于非直接(jie)短路和接(jie)池故(gu)障，用(yong)(yong)兆歐(ou)表遙測(ce)芯(xin)線間(jian)絕緣電阻(zu)或(huo)(huo)芯(xin)線對地(di)絕緣電阻(zu)，根據(ju)其阻(zu)值(zhi)可(ke)判定故(gu)障類型。
二、 電纜故障點的查找方(fang)法
1、 測聲(sheng)(sheng)(sheng)法(fa)所謂測聲(sheng)(sheng)(sheng)法(fa)就是根據故(gu)障(zhang)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)放電(dian)(dian)(dian)(dian)(dian)(dian)的聲(sheng)(sheng)(sheng)音(yin)(yin)(yin)進行查(cha)找(zhao)，該(gai)方(fang)法(fa)對于高(gao)(gao)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)芯(xin)線對絕緣層閃絡放電(dian)(dian)(dian)(dian)(dian)(dian)較(jiao)為(wei)(wei)有效。此方(fang)法(fa)所用(yong)(yong)(yong)設(she)備為(wei)(wei)直流(liu)(liu)耐壓(ya)(ya)試(shi)(shi)驗機。電(dian)(dian)(dian)(dian)(dian)(dian)路接線如圖(tu)1所示，其中SYB為(wei)(wei)高(gao)(gao)壓(ya)(ya)試(shi)(shi)驗變壓(ya)(ya)器，C為(wei)(wei)高(gao)(gao)壓(ya)(ya)電(dian)(dian)(dian)(dian)(dian)(dian)容器，ZL為(wei)(wei)高(gao)(gao)壓(ya)(ya)整流(liu)(liu)硅堆，R為(wei)(wei)限流(liu)(liu)電(dian)(dian)(dian)(dian)(dian)(dian)阻，Q為(wei)(wei)放電(dian)(dian)(dian)(dian)(dian)(dian)球間隙，L為(wei)(wei)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)芯(xin)線。當電(dian)(dian)(dian)(dian)(dian)(dian)容器C充電(dian)(dian)(dian)(dian)(dian)(dian)到(dao)一定(ding)電(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)(ya)值(zhi)時(shi)，球間隙對電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)故(gu)障(zhang)芯(xin)線放電(dian)(dian)(dian)(dian)(dian)(dian)，在(zai)故(gu)障(zhang)處(chu)(chu)電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)芯(xin)線對絕緣層放電(dian)(dian)(dian)(dian)(dian)(dian)產生"滋、滋"的火花放電(dian)(dian)(dian)(dian)(dian)(dian)聲(sheng)(sheng)(sheng)，再在(zai)雜噪(zao)聲(sheng)(sheng)(sheng)音(yin)(yin)(yin)最(zui)小的時(shi)候(hou)，借(jie)助耳(er)聾(long)助聽器或醫用(yong)(yong)(yong)聽診(zhen)器等音(yin)(yin)(yin)頻放大(da)設(she)備進行查(cha)找(zhao)。查(cha)找(zhao)時(shi)，將拾音(yin)(yin)(yin)器貼近地面(mian)，沿電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)走向慢(man)慢(man)移(yi)動，當聽到(dao)"滋、滋"放電(dian)(dian)(dian)(dian)(dian)(dian)聲(sheng)(sheng)(sheng)最(zui)大(da)時(shi)，該(gai)處(chu)(chu)即為(wei)(wei)故(gu)障(zhang)點。使用(yong)(yong)(yong)該(gai)方(fang)法(fa)一定(ding)要注意安(an)全，在(zai)試(shi)(shi)驗設(she)備端和電(dian)(dian)(dian)(dian)(dian)(dian)纜(lan)(lan)末端應設(she)專人(ren)監視。
2、 電(dian)(dian)橋法(fa)(fa)電(dian)(dian)橋法(fa)(fa)就是雙臂(bei)電(dian)(dian)橋測(ce)出電(dian)(dian)纜(lan)(lan)芯(xin)線(xian)的(de)(de)(de)直(zhi)(zhi)(zhi)流(liu)電(dian)(dian)阻(zu)(zu)(zu)(zu)值(zhi)(zhi)，再準確(que)測(ce)量(liang)(liang)(liang)電(dian)(dian)纜(lan)(lan)實際長(chang)(chang)度，按照電(dian)(dian)纜(lan)(lan)長(chang)(chang)度與(yu)電(dian)(dian)阻(zu)(zu)(zu)(zu)的(de)(de)(de)正比例(li)關系，計算(suan)的(de)(de)(de)故(gu)(gu)障(zhang)(zhang)點(dian)(dian)(dian)。該(gai)方法(fa)(fa)對于電(dian)(dian)纜(lan)(lan)芯(xin)線(xian)間(jian)(jian)直(zhi)(zhi)(zhi)接(jie)(jie)短(duan)路(lu)或(huo)短(duan)路(lu)點(dian)(dian)(dian)接(jie)(jie)觸電(dian)(dian)阻(zu)(zu)(zu)(zu)小于1Ω的(de)(de)(de)故(gu)(gu)障(zhang)(zhang)，判斷誤差(cha)一(yi)般不大(da)于3m，對于故(gu)(gu)障(zhang)(zhang)點(dian)(dian)(dian)接(jie)(jie)觸電(dian)(dian)阻(zu)(zu)(zu)(zu)大(da)于1Ω的(de)(de)(de)故(gu)(gu)障(zhang)(zhang)，可采用(yong)(yong)加高電(dian)(dian)壓燒穿的(de)(de)(de)方法(fa)(fa)使電(dian)(dian)阻(zu)(zu)(zu)(zu)降至1Ω以下(xia)(xia)，再按此(ci)方法(fa)(fa)測(ce)量(liang)(liang)(liang)。測(ce)量(liang)(liang)(liang)電(dian)(dian)路(lu)如圖(tu)2所示(shi)，首先測(ce)出芯(xin)線(xian)a與(yu)b之間(jian)(jian)的(de)(de)(de)電(dian)(dian)阻(zu)(zu)(zu)(zu)R1，則(ze)R1=2RX+R，其中(zhong)(zhong)R為(wei)a相或(huo)b相至故(gu)(gu)障(zhang)(zhang)點(dian)(dian)(dian)的(de)(de)(de)一(yi)相電(dian)(dian)阻(zu)(zu)(zu)(zu)值(zhi)(zhi)，R為(wei)短(duan)接(jie)(jie)點(dian)(dian)(dian)的(de)(de)(de)接(jie)(jie)觸電(dian)(dian)阻(zu)(zu)(zu)(zu)。再就電(dian)(dian)纜(lan)(lan)的(de)(de)(de)另一(yi)端(duan)測(ce)出a'和b'芯(xin)線(xian)間(jian)(jian)的(de)(de)(de)直(zhi)(zhi)(zhi)流(liu)電(dian)(dian)阻(zu)(zu)(zu)(zu)值(zhi)(zhi)R2，則(ze)R2=2R(L-X)+R，式(shi)(shi)中(zhong)(zhong)R(L-X)為(wei)a'相和b'相芯(xin)線(xian)至故(gu)(gu)障(zhang)(zhang)點(dian)(dian)(dian)的(de)(de)(de)一(yi)相電(dian)(dian)阻(zu)(zu)(zu)(zu)值(zhi)(zhi)。測(ce)完R1與(yu)R2后，再按圖(tu)3所示(shi)電(dian)(dian)路(lu)將(jiang)b'與(yu)C'短(duan)接(jie)(jie)，測(ce)出b、c兩相芯(xin)線(xian)間(jian)(jian)的(de)(de)(de)直(zhi)(zhi)(zhi)流(liu)電(dian)(dian)阻(zu)(zu)(zu)(zu)值(zhi)(zhi)，則(ze)該(gai)阻(zu)(zu)(zu)(zu)值(zhi)(zhi)的(de)(de)(de)1/2為(wei)每相芯(xin)線(xian)的(de)(de)(de)電(dian)(dian)阻(zu)(zu)(zu)(zu)值(zhi)(zhi)，用(yong)(yong)RL表示(shi)。RL=RX+R(L-X)，由此(ci)可得出故(gu)(gu)障(zhang)(zhang)點(dian)(dian)(dian)的(de)(de)(de)接(jie)(jie)觸電(dian)(dian)阻(zu)(zu)(zu)(zu)值(zhi)(zhi)：R=R1+R2-2RL。因此(ci)，故(gu)(gu)障(zhang)(zhang)點(dian)(dian)(dian)兩側芯(xin)線(xian)的(de)(de)(de)電(dian)(dian)阻(zu)(zu)(zu)(zu)值(zhi)(zhi)可用(yong)(yong)下(xia)(xia)式(shi)(shi)表示(shi)：RX=(R1-R)/2，R(L-X)=(R2-R)/2。RX、R(L-X)、RL三個數值(zhi)(zhi)確(que)定后，按比例(li)公式(shi)(shi)即可求出故(gu)(gu)障(zhang)(zhang)點(dian)(dian)(dian)距(ju)電(dian)(dian)纜(lan)(lan)端(duan)頭的(de)(de)(de)距(ju)離X或(huo)(L-X)：X=(RX/RL)L，(L-X)=(R(L-X)/RL)L，式(shi)(shi)中(zhong)(zhong)L為(wei)電(dian)(dian)纜(lan)(lan)的(de)(de)(de)總長(chang)(chang)度。采用(yong)(yong)電(dian)(dian)橋法(fa)(fa)時應保(bao)證測(ce)量(liang)(liang)(liang)精度，電(dian)(dian)橋連(lian)接(jie)(jie)線(xian)要盡量(liang)(liang)(liang)短(duan)，經徑要足夠大(da)，與(yu)電(dian)(dian)纜(lan)(lan)芯(xin)線(xian)連(lian)接(jie)(jie)要采用(yong)(yong)壓接(jie)(jie)或(huo)焊摟，計算(suan)過(guo)程中(zhong)(zhong)小數位(wei)要全部保(bao)留。
3、電(dian)容電(dian)流測定(ding)法電(dian)纜(lan)在運(yun)行(xing)中(zhong)，芯線(xian)(xian)之間、芯線(xian)(xian)對地都存在電(dian)容，該電(dian)容是(shi)均勻(yun)分(fen)布(bu)的(de)，電(dian)容量與電(dian)纜(lan)長度呈線(xian)(xian)性(xing)比例關系(xi)，電(dian)容電(dian)流測定(ding)法就是(shi)根據這一(yi)原理進(jin)行(xing)測定(ding)的(de)，對于電(dian)纜(lan)芯線(xian)(xian)斷線(xian)(xian)故障的(de)測定(ding)非常準確(que)。測量電(dian)路如圖4所(suo)示，使用設備(bei)為1～2kVA單相調壓(ya)器一(yi)臺，0～30V、0.5級(ji)(ji)交(jiao)流電(dian)壓(ya)表一(yi)只，0～100mA、0.5級(ji)(ji)交(jiao)流毫安表一(yi)只。
測量步驟：
(1)首先在電(dian)纜首端分別測(ce)出每(mei)芯線的電(dian)容電(dian)流(應(ying)保(bao)持施加電(dian)壓相等)Ia、Ib、Ic的數值。
(2)在電(dian)纜(lan)的(de)(de)(de)末端再測量每相(xiang)芯線(xian)的(de)(de)(de)電(dian)容電(dian)流Ia'、Ib'、Ic'的(de)(de)(de)數(shu)值，以核對完好芯線(xian)與斷(duan)線(xian)芯線(xian)的(de)(de)(de)比(bi)容之比(bi)，初步可判斷(duan)出斷(duan)線(xian)距離近(jin)似(si)點(dian)。
(3)根據電(dian)(dian)(dian)(dian)容量(liang)(liang)計算公式C=1/2πfU可知，在電(dian)(dian)(dian)(dian)壓(ya)(ya)U、頻率(lv)(lv)f不變時C與I成正比(bi);因為(wei)工頻電(dian)(dian)(dian)(dian)壓(ya)(ya)的(de)f(頻率(lv)(lv))不變，測量(liang)(liang)時只要保(bao)證施加電(dian)(dian)(dian)(dian)壓(ya)(ya)不變，電(dian)(dian)(dian)(dian)容電(dian)(dian)(dian)(dian)流之比(bi)即為(wei)電(dian)(dian)(dian)(dian)容量(liang)(liang)之比(bi)。設電(dian)(dian)(dian)(dian)纜全長(chang)L，芯線斷線點距離(li)為(wei)x，則Ia/Ic=L/x，x=(Ic/Ia)L。測量(liang)(liang)過(guo)程中(zhong)，只要保(bao)證電(dian)(dian)(dian)(dian)壓(ya)(ya)不變，電(dian)(dian)(dian)(dian)流表讀數準確(que)，電(dian)(dian)(dian)(dian)纜總(zong)長(chang)度(du)測量(liang)(liang)精確(que)，其測定(ding)誤差(cha)比(bi)較小。
4、零(ling)電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)法(fa)(fa)零(ling)電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)法(fa)(fa)也(ye)就是電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)比較(jiao)法(fa)(fa)，它適應于(yu)(yu)長度較(jiao)短的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)纜芯線對(dui)地故(gu)障，應用(yong)此(ci)方法(fa)(fa)測量(liang)簡便精確，不需(xu)要精密(mi)儀器和(he)(he)復雜計算(suan)。測量(liang)原理如下(xia)：將電(dian)(dian)(dian)(dian)(dian)(dian)纜故(gu)障芯線與等長的(de)(de)(de)(de)(de)比較(jiao)導(dao)線并聯，在兩端加壓(ya)E時(shi)，相(xiang)當于(yu)(yu)在兩個并聯的(de)(de)(de)(de)(de)均勻電(dian)(dian)(dian)(dian)(dian)(dian)阻絲(si)兩端接了電(dian)(dian)(dian)(dian)(dian)(dian)源。此(ci)時(shi)，一(yi)條電(dian)(dian)(dian)(dian)(dian)(dian)阻絲(si)上的(de)(de)(de)(de)(de)任(ren)何一(yi)點(dian)(dian)(dian)和(he)(he)另一(yi)條電(dian)(dian)(dian)(dian)(dian)(dian)阻絲(si)上的(de)(de)(de)(de)(de)對(dui)應點(dian)(dian)(dian)之間的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)差必(bi)然為零(ling)。反之，電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)差為零(ling)的(de)(de)(de)(de)(de)兩點(dian)(dian)(dian)必(bi)然是對(dui)應點(dian)(dian)(dian)，因(yin)為微(wei)伏表的(de)(de)(de)(de)(de)負極接地，與電(dian)(dian)(dian)(dian)(dian)(dian)纜故(gu)障點(dian)(dian)(dian)等電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)，所以，當微(wei)伏表的(de)(de)(de)(de)(de)正極在比較(jiao)導(dao)電(dian)(dian)(dian)(dian)(dian)(dian)上移動至示值為零(ling)時(shi)的(de)(de)(de)(de)(de)點(dian)(dian)(dian)與故(gu)障點(dian)(dian)(dian)等電(dian)(dian)(dian)(dian)(dian)(dian)位(wei)(wei)，即故(gu)障點(dian)(dian)(dian)的(de)(de)(de)(de)(de)對(dui)應點(dian)(dian)(dian)。
測量步驟如下：
(1)先(xian)在(zai)(zai)b和c相芯線(xian)上接上電池E，再在(zai)(zai)地面上敷設一根與故(gu)障電纜長(chang)度(du)相等的比(bi)較導線(xian)S，該導線(xian)要用(yong)裸銅(tong)線(xian)或裸鋁線(xian)，其截面應相等，不(bu)能有(you)中間(jian)接頭。
(2)將微伏表的負極接地(di)，正極接一根較(jiao)長的軟導線，導線另一端要求在(zai)敷設的比較(jiao)導線上(shang)滑動時能(neng)充分(fen)接觸(chu)。
(3)合上(shang)閘刀(dao)開關K，將軟導線的斷頭(tou)在比較導線上(shang)滑(hua)動，當(dang)微伏(fu)表指示為(wei)零時的位(wei)置即為(wei)電纜(lan)故障(zhang)點的位(wei)置。
