变压器直流电阻测试原理及现场缺陷情况分析

变压器绕组的直流电阻可反映出绕组接头焊接质量的好坏、绕组有无匝间短路、分接开关是否良好、导线是否断股等情况。笔者介绍了测量直流电阻的原理、常用测试方法及现场发现直阻超标的一般处理原则。之后,分析并总结了深圳局近几年发生的数起由不同故障引起的变压器直流电阻测试结果超标的事故。一般情况下,若变压器某相发生匝间短路则该相直流电阻减小,若焊接不良或发生断股,则该相的直流电阻值增大,分接开关故障视故障类型而定。当测试结果异常时应先进行综合分析,与往年的数据比较,排除干扰,同时结合其他绝缘监督试验,以便对故障类型和故障位置做出更为准确可靠的判断。

Theoretic of Testing Direct Current Resistance and Analysis of Different kind of Defects in Field

Several kinds of transformer defects such as turn-to-turn short circuit,poor contact,can be judged by the result of the winding direct current(DC) resistance test.The theoretic and the methods to test DC Resistance,as well as the principle to deal with test results of exceeding rate have been explained in this paper.Then analysis based on different kinds of defects in field has been made.When turn-to-turn short circuit happened,the winding DC resistance would decrease;while poor contact happened between conductors,the winding DC resistance would increase.The importance and availability of testing deformation of transformers has been proved by a lot of experiments in substations.Combined with other electric test,the result can be much more effective in judging the situation of transformers.