负极性直流下金属微粒对SF_6中支柱绝缘子闪络特性的影响

Influence of Metallic Particle on Flashover Characteristics of Post Insulator in SF_6 Under Negative DC Voltage

金属微粒是导致气体绝缘金属封闭输电线路(gas insulated transmission line,GIL)绝缘子闪络的重要原因之一。为研究金属微粒对支柱绝缘闪络特性的影响,搭建了实验平台,研究了负极性直流下气压、金属导电微粒尺寸及位置对SF6中支柱绝缘子闪络特性的影响,对闪络过程进行了分析,并应用有限元分析软件对表面电场分布情况进行了计算。结果表明:当绝缘子表面存在金属微粒时,绝缘子闪络电压随气压增大会出现极大值,此现象主要与空间电荷的分布有关;金属微粒附着于高压导体侧时,闪络电压随金属微粒长度增加明显降低,当微粒长度超过一定值时,闪络电压下降减缓;微粒位于绝缘子金属电极侧时对绝缘水平影响最大,随着金属微粒远离高压电极,闪络电压先上升后降低。

The flashover of insulators is a bottleneck for the development of gas insulated transmission line （GIL）. The operation experience of GIL shows that metallic particle plays an important role in flashover of the insulator. An experiment platform was established to study the influence of gas pressure on the flashover characteristics of the post insulator in SF6 under negative DC voltage. The impacts that the position and size of a metallic particle had on flashover characteristics were also studied. The distribution of electric field was processed by the finite element analysis software. The results indicate that the flashover voltage reaches the maximum value with the increase of gas pressure. This phenomenon is connected with the distribution of space charge. The flashover voltage drops rapidly when the metallic particle is attached to its high voltage electrode. The reduction of flashover voltage will become slow when the metallic particle’s length extends a certain value. The metallic particle will cause the greatest threat to insulation level when it is attached to the electrode of post insulator. The flashover voltage increases at first and then decreases when the distance between the metallic particle and high voltage electrode increases. The process of flashover was analyzed in the aspect of distribution of electric field.