測(ce)試(shi)中常用的(de)兩(liang)種(zhong)測(ce)試(shi)設備有兩(liang)種(zhong)：直(zhi)流(liu)雙(shuang)臂(bei)電(dian)橋和變壓(ya)(ya)器(qi)(qi)直(zhi)流(liu)電(dian)阻。然(ran)而，一些(xie)測(ce)試(shi)人(ren)員對(dui)試(shi)驗(yan)(yan)儀器(qi)(qi)的(de)性能參數(shu)(shu)不了解(jie)，導致測(ce)試(shi)數(shu)(shu)據不準確，甚至(zhi)造(zao)成被測(ce)試(shi)變壓(ya)(ya)器(qi)(qi)的(de)故(gu)障。本文(wen)就變壓(ya)(ya)器(qi)(qi)直(zhi)流(liu)電(dian)阻試(shi)驗(yan)(yan)中的(de)儀表(biao)選(xuan)用及(ji)應注意的(de)問題作(zuo)一簡(jian)單的(de)說明。

ZCZR-5A直流電阻測試儀

　　直流雙臂電橋和直流電阻測試儀介紹

　　直(zhi)(zhi)(zhi)流電(dian)(dian)橋(qiao)(qiao)(qiao)(qiao)是(shi)利用(yong)已(yi)(yi)知(zhi)和未知(zhi)（待測(ce)）的(de)(de)(de)電(dian)(dian)阻組成的(de)(de)(de)電(dian)(dian)橋(qiao)(qiao)(qiao)(qiao)電(dian)(dian)路，通(tong)過比較法(fa)測(ce)量試品的(de)(de)(de)直(zhi)(zhi)(zhi)流電(dian)(dian)阻的(de)(de)(de)的(de)(de)(de)一種(zhong)試驗儀器。我們將電(dian)(dian)橋(qiao)(qiao)(qiao)(qiao)兩個(ge)臂接(jie)入(ru)被測(ce)量，另兩個(ge)臂為已(yi)(yi)知(zhi)固定(ding)電(dian)(dian)阻的(de)(de)(de)電(dian)(dian)橋(qiao)(qiao)(qiao)(qiao)稱為雙臂直(zhi)(zhi)(zhi)流電(dian)(dian)橋(qiao)(qiao)(qiao)(qiao)（也叫凱(kai)爾文電(dian)(dian)橋(qiao)(qiao)(qiao)(qiao)）。電(dian)(dian)橋(qiao)(qiao)(qiao)(qiao)只有一個(ge)臂接(jie)入(ru)被測(ce)量，其(qi)它三個(ge)臂為已(yi)(yi)知(zhi)固定(ding)電(dian)(dian)阻的(de)(de)(de)稱為單(dan)臂電(dian)(dian)橋(qiao)(qiao)(qiao)(qiao)（也叫惠斯通(tong)電(dian)(dian)橋(qiao)(qiao)(qiao)(qiao)）。

　　直(zhi)流電(dian)(dian)阻測試(shi)(shi)儀(yi)主(zhu)要是利用雙臂電(dian)(dian)橋的(de)(de)原理，通(tong)過高(gao)精度程(cheng)控(kong)整流穩壓電(dian)(dian)源，自動完成直(zhi)流電(dian)(dian)阻的(de)(de)充電(dian)(dian)、測試(shi)(shi)、放電(dian)(dian)、記(ji)數過程(cheng)的(de)(de)一種試(shi)(shi)驗儀(yi)器。具有操作簡單、測量速度快等優點。

　　直流電阻測試中儀器的選擇

　　變壓器由于其構造的原因，一般繞組電感很大，而繞組的電阻很小。因此，變壓器直流電阻測試，都需要克服變壓器繞組電感的感電勢的影響，所以就存在一個充電的過程，其實際就是克服感性元件的影響的過程。而變壓器容量越大，其電感就越大，需要的試驗儀器試驗電源的容量就越大。我們選擇的試驗儀器的充電容量和電流的大小就決定了，充電過程的長短和試驗結果精度的高低。因此，我們按照變壓器的容量的大小來說明變壓器直流電阻測試儀器的選擇。

　　大(da)容(rong)量(liang)變(bian)壓(ya)器(qi)的(de)(de)(de)(de)(de)直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)測(ce)試(shi)中有兩個主要的(de)(de)(de)(de)(de)特(te)(te)(te)點：一(yi)、是(shi)繞組(zu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)特(te)(te)(te)別小，二、是(shi)繞組(zu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)大(da)。首先，考慮(lv)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)的(de)(de)(de)(de)(de)影響(xiang)，如(ru)果使(shi)用(yong)便攜式型雙(shuang)(shuang)臂(bei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)橋來(lai)測(ce)，由于其試(shi)驗電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源只(zhi)有幾伏的(de)(de)(de)(de)(de)干電(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)，充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)都是(shi)毫安(an)級(ji)的(de)(de)(de)(de)(de)，那么其充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程肯定會很長。對于像電(dian)(dian)(dian)(dian)(dian)(dian)(dian)爐(lu)、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)解(jie)鋁等使(shi)用(yong)的(de)(de)(de)(de)(de)超(chao)(chao)大(da)容(rong)量(liang)的(de)(de)(de)(de)(de)整(zheng)流(liu)變(bian)壓(ya)器(qi)，一(yi)般電(dian)(dian)(dian)(dian)(dian)(dian)(dian)沒充完，試(shi)驗電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源已經沒電(dian)(dian)(dian)(dian)(dian)(dian)(dian)了(le)。因此，就需要選擇充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)大(da)，通過外(wai)接(jie)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源整(zheng)流(liu)穩(wen)壓(ya)來(lai)充電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)(de)(de)直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)測(ce)試(shi)儀(yi)(yi)來(lai)完成。再者，考慮(lv)繞組(zu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)特(te)(te)(te)別小（例(li)如(ru)35kV 18000KVA的(de)(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)爐(lu)變(bian)壓(ya)器(qi)二次繞組(zu)的(de)(de)(de)(de)(de)0.0000590Ω），超(chao)(chao)出了(le)便攜式雙(shuang)(shuang)臂(bei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)橋的(de)(de)(de)(de)(de)測(ce)量(liang)范圍(wei)(wei)0.0001～11Ω，同時也(ye)會超(chao)(chao)出了(le)許多直流(liu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)測(ce)試(shi)儀(yi)(yi)的(de)(de)(de)(de)(de)測(ce)量(liang)范圍(wei)(wei)，在(zai)不想增加購(gou)買設備(bei)費(fei)用(yong)的(de)(de)(de)(de)(de)情(qing)況下，可選用(yong)測(ce)量(liang)原理和雙(shuang)(shuang)臂(bei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)橋一(yi)致的(de)(de)(de)(de)(de)100A的(de)(de)(de)(de)(de)回路電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)測(ce)試(shi)儀(yi)(yi)（測(ce)量(liang)范圍(wei)(wei)0-1mΩ）來(lai)完成試(shi)驗。

ZC-205B三通道直流電阻測試儀

　　特別小容量的(de)變(bian)壓(ya)(ya)器(qi)(qi)像所用變(bian)壓(ya)(ya)器(qi)(qi)等(deng)，其(qi)繞組(zu)電感(gan)相對于大容量變(bian)壓(ya)(ya)器(qi)(qi)很(hen)小，便(bian)攜式雙(shuang)臂(bei)電橋和直(zhi)流電阻(zu)測(ce)(ce)試(shi)儀(yi)都能(neng)很(hen)容易完成充電、測(ce)(ce)量。但(dan)是這種變(bian)壓(ya)(ya)器(qi)(qi)也有(you)自己(ji)的(de)特點：一(yi)、電阻(zu)比較大，有(you)的(de)會超(chao)出(chu)便(bian)攜式QJ44型雙(shuang)臂(bei)電橋的(de)測(ce)(ce)量范圍(wei)，比如干(gan)式10/0.4kV 63KVA變(bian)壓(ya)(ya)器(qi)(qi)的(de)高(gao)(gao)壓(ya)(ya)繞組(zu)電阻(zu)值一(yi)般都在二十幾歐姆。只能(neng)使(shi)用直(zhi)流電阻(zu)測(ce)(ce)試(shi)儀(yi)。二、額定(ding)電流小，比如干(gan)式10/0.4kV 63KVA變(bian)壓(ya)(ya)器(qi)(qi)的(de)高(gao)(gao)壓(ya)(ya)繞組(zu)的(de)額定(ding)電流為3.64A。低于許多直(zhi)流電阻(zu)測(ce)(ce)試(shi)儀(yi)的(de)試(shi)驗電流，此時我們需要用高(gao)(gao)精度萬用表來完成測(ce)(ce)試(shi)，也可以用合適的(de)單(dan)臂(bei)電橋來完成試(shi)驗。

　　對于(yu)中等容量的變壓器，我(wo)們(men)可以用直(zhi)流電阻測試(shi)(shi)儀和便攜式QJ44型(xing)雙臂電橋都可完成(cheng)繞組直(zhi)流電阻的測試(shi)(shi)。不過為了試(shi)(shi)驗快速(su)，我(wo)們(men)最好(hao)使用直(zhi)流電阻測試(shi)(shi)儀來完成(cheng)試(shi)(shi)驗。

　　直流電阻測試中的需要注意的問題

　　首先，需要根據變壓(ya)器銘牌(pai)數(shu)據和出廠試(shi)驗報告(gao)選擇合適的(de)試(shi)驗儀器。主要考慮變壓(ya)器的(de)容量、繞組(zu)阻(zu)值大小、繞組(zu)額定電流，試(shi)驗儀器的(de)精(jing)度、量程、試(shi)驗電流，二者要匹配。

　　其次，選好試驗(yan)儀器(qi)后，需要(yao)用標準電阻(zu)對直流電阻(zu)測試儀器(qi)檢(jian)查其測量(liang)準確度后，決(jue)定該儀器(qi)能(neng)否(fou)使用。

　　最后，開(kai)始試驗時去掉變壓器(qi)繞(rao)組引(yin)出線(xian)接線(xian)柱上的(de)螺(luo)母，檢查油浸變壓器(qi)的(de)檔位(wei)放到對(dui)應(ying)檔位(wei)的(de)卡槽保證接觸(chu)良(liang)好(hao)，將干式變壓器(qi)的(de)組別連接桿的(de)連接螺(luo)栓緊固保證接觸(chu)良(liang)好(hao)

ZRCS-10A型變(bian)壓(ya)器直流電阻測試(shi)儀