不同覆冰类型绝缘子串的泄漏电流特征分析

Characteristic Analysis of Leakage Current of Insulator Strings Under Different Icing Types

对绝缘子泄漏电流的分析是进行覆冰闪络预警的一个重要方法,而绝缘子的泄漏电流特征除与绝缘子串本身特性有关之外,还受到覆冰类型的影响。对玻璃绝缘子进行人工覆冰试验,研究了雨凇、混合凇和雾凇条件下,绝缘子在覆冰期和融冰期的泄漏电流变化趋势,以及不同阶段冰层电阻变化规律;通过FFT分析,研究了泄漏电流的谐波组成和阻性容性分量在融覆冰不同阶段的分布规律,定义了用于定量评价绝缘子覆冰状态的融覆冰状态判定系数。研究结果表明,泄漏电流在覆冰期没有显著变化,在融冰前期迅速上升,中后期保持平稳或略有上升;覆冰期冰层电阻与覆冰类型关系不大,融冰期雾凇和混合凇电阻小于雨凇。覆冰绝缘子泄漏电流主要成分为基波分量,基波阻性分量和容性分量与全电流比值的相对大小关系不同时,绝缘子表面冰层状态不同,从而据此判定绝缘子所处的融覆冰状态,对覆冰闪络进行预警。

Leakage current analysis on insulator is an important method for early-warning of icing flashover.Characteristics of insulator leakage current are affected by both icing type and characteristics of insulator string.This paper presented artificial icing on glass insulators in research of trend of leakage current and change rule of ice resistance in icing and melting stages of glaze,hard rime and soft rime.With FFT analysis,harmonic components and distribution of resistive and capacitive components of leakage current in different stages of icing and melting were studied.Icing state judgment factor was defined for quantitative evaluation of insulator icing state.Results showed that leakage current in icing period did not change significantly.However,it increased rapidly in initial period of melting process,and kept flat or rose slightly in middle and final periods of melting.Icing type had little effect on ice resistance in icing period.In melting period,resistance of hard rime and soft rime was lower than that of glaze.The main component of ice-covered insulators＇ leakage current was fundamental component.When relative value between fundamental resistive and fundamental capacitive components to total fundamental current is different,the icing state on the insulator is different,thus helping to judge the icing state on the insulator and make early-warning of flashover.