影響絕緣電阻的因素主要有以下幾個方面：
一、溫度的影響
運行中的電力設備其溫度隨周圍環境變化，其絕緣電阻也是隨溫度而變化的。一般情況下，絕緣電阻隨溫度升高而降低。原因在于溫度升高時，絕緣介質內部離子、分子運動加劇，絕緣物內的水分及其中含有的雜質、鹽分等物質也呈擴散趨勢，使電導增加，絕緣電阻降低。這與導體的電阻隨溫度的變化是不一樣的。不同的電力設備及不同材料制成的電力設備，其絕緣電阻隨溫度的變化也不一樣，現場測童也很難保證在*近似的溫度下進行。為了進行試驗結果比較，有關單位曾給出一些設備的溫度換算系數，但由于設備的陳舊程度、干燥程度，使用的測溫方法等影響因素很多，很難得出一個準確的換算系數。因此實際測量絕緣電阻時，必須記錄試驗溫度（環境溫度及設備本體溫度），而且盡可能在相近溫度下進行測量，以避免溫度換算引起的誤差。
二、濕度和電力設備表面臟污的影響
電力設備周圍環境濕度的變化及空氣污染造成的表面臟污對絕緣電阻影響很大。空氣相對濕度增大時，絕緣物表面吸附許多水分，使表面電導率增加，絕緣電阻降低。當絕緣物表面形成連通水膜時，絕緣電阻更低。如雨后測得一組220kV磁吹避雷器的絕緣電阻僅為2000MΩ；當屏蔽掉其表面電流時，絕緣電阻為1000MΩ以上；第二天下午晴天，在表面干燥狀態下測量其絕緣電阻也在1000MΩ以上。電力設備的表面臟污也使設備表面電阻大大降低，絕緣電阻顯著下降。根據以上兩種情況，現場測量絕緣電阻時都必須用屏蔽環消除表面泄漏電流的影響或烘干、清擦干凈設備表面，以得到真實的測量值。
三、殘余電荷的影響
大容(rong)量設備(bei)運(yun)行中(zhong)(zhong)的(de)(de)(de)殘(can)(can)余電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)或試驗中(zhong)(zhong)形成的(de)(de)(de)殘(can)(can)余電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)未(wei)*放(fang)(fang)(fang)盡(jin)，會造成絕緣(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)偏大或偏小(xiao)(xiao)，引起測得(de)(de)的(de)(de)(de)絕緣(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)不(bu)真(zhen)(zhen)實。殘(can)(can)余電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)的(de)(de)(de)性與兆歐表(biao)的(de)(de)(de)性相(xiang)同(tong)時(shi)，測得(de)(de)的(de)(de)(de)絕緣(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)將比(bi)真(zhen)(zhen)實值增大；殘(can)(can)余電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)的(de)(de)(de)性與兆歐表(biao)的(de)(de)(de)性相(xiang)反(fan)時(shi)，測得(de)(de)的(de)(de)(de)絕緣(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)將比(bi)真(zhen)(zhen)實值減小(xiao)(xiao)。原因在于(yu)性相(xiang)同(tong)時(shi)，由于(yu)同(tong)性相(xiang)斥，兆歐表(biao)輸出較(jiao)少電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)；性相(xiang)反(fan)時(shi)，兆歐表(biao)要輸出更多(duo)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)去(qu)中(zhong)(zhong)和殘(can)(can)余電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)。為消除(chu)殘(can)(can)余電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)的(de)(de)(de)影(ying)響，測量絕緣(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)前必須充(chong)分(fen)接地放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，重復側量中(zhong)(zhong)也(ye)應充(chong)分(fen)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)，大容(rong)量設備(bei)應至(zhi)少放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)5min。如一(yi)大容(rong)量變壓器，充(chong)分(fen)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)后(hou)*次(ci)測得(de)(de)其尸個(ge)繞組的(de)(de)(de)絕緣(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)為4000MΩ，第(di)二次(ci)再測同(tong)一(yi)繞組（未(wei)充(chong)分(fen)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)），絕緣(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)為5000MΩ，宛分(fen)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)10min后(hou)第(di)三次(ci)測量，其絕緣(yuan)(yuan)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)為4000MΩ。