摘 要:污闪是电力系统安全运行的严重威胁，提取污秽绝缘子泄漏电流特征量是有效实现污闪预警的前提之一，目前污闪预警并不十分理想的原因之一是表征污闪与泄漏电流关系的特征量尚未达成共识。以人工污秽试验为基础，结合交流下污秽绝缘子表面电弧放电机制，分析了盐密和湿度(relative humidity，RH)对绝缘子表面泄漏电流相位(θ )的影响，泄漏电流的总谐波畸变率(total harmonic distortion，THD)、高次谐波和低次谐波与泄漏电流波形畸变之间的内在联系。结果表明：θ 随RH 的增加而减小；泄漏电流波形畸变的主要原因是电弧放电产生的3 次谐波，轻污时THD随RH 的增加而缓慢增加，污秽较重时THD 随RH 的增加呈先减小后增加的趋势，存在极小值，在THD 极小值处，污秽绝缘子开始产生局部放电现象。根据理论分析和试验验证，提出可利用θ 和THD 的变化趋势在空气湿度较低时进行污闪预警。
关键词：泄漏电流 污秽绝缘子 相对湿度 相位 总谐波畸变率
ABSTRACT:The flashover of polluted insulators greatly threatens security of the power system. One of the preconditions for flashover prediction is to obtain the effective leakage current characteristics of polluted insulators, but there is still no consensus achieved on the relation between the flashover and leakage current characteristics, which is one of the reasons for imperfect flashover prediction system. Based on the AC flashover model, the phase (θ ) of leakage current has been studied under different relative humidity (RH) and salt deposit density (SDD) according to artificial pollution tests, and the relationships among the waveform distortion of leakage current, total harmonic distortion (THD), low frequency harmonic components and high frequency harmonic components were analyzed. It has been found that θ decreases with the increasing of RH. The main cause of the waveform distortion of leakage current is the third harmonic when arc discharge appears. The THD increases slowly with the increasing of RH under light contamination, while the THD decreases firstly then increases with the increasing of RH under moderate and heavy contamination; there is a minimum value to THD, and discharge appears on the surface of insulators when THD becomes the minimum value. Consequently, the THD and θ can be used to predict the flashover under low RH according to the theoretical analysis and test results.
Keywords: leakage current；polluted insulator；relative humidity；phase；total harmonic distortion
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