极不均匀染污绝缘子操作冲击闪络特性

Switching Impulse Flashover Characteristics of Insulator with Extremely Non-uniform Pollution

输电线路绝缘子在运行一段时间后,其上、下表面呈现出不均匀染污现象,将对绝缘子操作冲击闪络电压造成较大影响。该文采用湿污法模拟绝缘子上/下表面不均匀染污,在不同盐密下,对干净、均匀染污和极不均匀染污XP–70和LXY–70两类绝缘子,进行预加和非预加的操作冲击闪络试验,分析其闪络特性;使用超高速摄像机对XP–70绝缘子操作冲击闪络过程进行拍摄并分析其放电机理。结果表明,极不均匀染污绝缘子操作冲击闪络电压与上、下表面盐密之比(T/B)呈负相关,且随等值盐密的增加而减小;交流电压预加也会显著减小闪络电压。此外,极不均匀染污绝缘子操作冲击闪络形式为沿面分段依次闪络,放电发展速度相较于均匀污秽时更快,闪络时间更短,发展轨迹存在电弧短接伞裙和钢脚现象。该结果可为复杂极端环境下的输电线路外绝缘设计提供理论支持,对绝缘子的防污闪工作具有重要的指导意义。

After a period of operation,transmission line insulators show non-uniform pollution on their upper and lower surfaces.The pollution has a great impact on the switching impulse flashover voltage of the insulator.In this paper,the wet-pollution method is used to simulate the non-uniform pollution on the upper/lower surface of insulators.The flashover characteristics of clean,uniform,and extremely non-uniform pollution of XP–70 and LXY–70 insulators are analyzed by switching impulse flashover tests in the presence and absence of pre-addition voltage at different salt densities.An ultra-high-speed camera is used to photograph the switching impulse flashover process of XP–70 insulators.The results show that the switching impulse flashover voltage of insulators with extremely non-uniform pollution is negatively correlated with the ratio of upper and lower surface salt density(T/B),and decreases with the increase of equivalent salt density.The pre-addition voltage will also significantly reduce the flashover voltage.In addition,the insulators with extremely non-uniform pollution switching impulse flashover are in the form of sequential flashover along the face segment.The discharge development speed is faster compared to uniform pollution,flashover time is shorter,while arc connection umbrella skirt and steel foot phenomenon exists in the development of trajectory.The results can provide theoretical supports for the design of external insulation of transmission lines in complex and extreme environments,and are an important guideline for the prevention of pollution and flashover of insulators.