低气压下直流绝缘子串污闪过程中局部电弧发展特性

Propagation of Partial Arc During the DC Pollution Flashover Process for Insulator String at Low Air Pressure

绝缘子污秽闪络事故严重威胁电力系统的安全可靠运行,目前国内外对污闪机理的研究主要是以平板模型为基础的,而研究污闪机理的关键是研究局部电弧形成后如何发展成完全闪络。开展低气压下绝缘子串直流污闪过程中局部电弧发展研究,结果表明:低气压下绝缘子串直流污闪过程中局部电弧发展中存在飘弧现象,即局部电弧由沿面电弧和空气间隙电弧2部分组成;低气压下局部电弧的发展主要决定于静电力和热浮力,静电力和热浮力随气压变化的规律存在差异,使得低气压下染污绝缘子串局部电弧的飘弧更严重;低气压下染污绝缘子串直流污闪过程中局部电弧的发展缓慢,局部电弧发展长度为绝缘子串闪络距离的60%以内时,局部电弧的发展速度小于10m/s,在最后闪络阶段,局部电弧的发展速度剧增至30～80m/s,绝缘子串的最终闪络不是电击穿的原因。

Pollution flashover accidents of insulators may threaten the operation safety of power system. The key of the research on pollution mechanism is how the partial arc propagates to flashover, and it has been based on plate model by now. The propagation of partial arc under low air pressure during the DC pollution flashover process of insulator is researched. The results suggest that some of the partial arcs may deviate from the surface of polluted insulator string and form the air gap arc during the pollution flashover process. The partial arcs include two main parts： air gap arcs and surface arcs during the flashover process for the polluted insulator string. It was found that the propagation of partial arc depends on the electrostatic force and thermal buoyant force under low air pressure and the difference between influences of air pressure on electrostatic force and thermal buoyant force makes the partial arc deviate from the surface of insulator more severely at high altitude. When the length of partial arc is in 60 percent of the total leakage distance, the propagation speed of partial arc is slow which is in 10 m/s and may reach 30-80 m/s at the end of flashover stage during the pollution flashover process at low air pressure, so the main reason leading to pollution insulator flashover at last is not electric breakdown.