操作冲击电压下空间电荷对棒—线间隙放电的影响

Influence of Space Charge on Air Gap Discharge Under Switching Impulse

绕击是造成超特高压输电线路雷击跳闸的主要原因,而在绕击事故中,空间电荷的作用不容忽视。为研究空间电荷对雷电绕击输电线路的影响,笔者对150 cm棒—线间隙施加正负操作冲击电压,采用高速摄像系统对放电发展过程进行观测并对外径不同的线电极上的击中次数进行了统计分析,测量了棒对不同外径线电极的预放电电流,采用积分电流法得到线电极周围的空间电荷量,通过ANSYS仿真得到空间电荷对电场的影响。实验结果发现:正操作冲击电压下空间电荷的屏蔽作用对放电击中点的影响较大,而负操作冲击电压下,空间电荷的屏蔽作用不是影响击中次数和放电路径的主导因素;空间电荷的屏蔽作用与线电极的尺寸有关,线电极的外径越大,其表面空间电荷的屏蔽作用越小。

Shielding failure is the main factor for lightning trip-out of EHV and UHV transmission lines, and space charge plays an important role in the shielding failure accident. In order to investigate the influence of space charge on lightning discharge, a rod-line air gap of 150 cm in length was set up. Under the positive and negative switching impulse voltage, the discharge process of the gap was observed by a high speed video camera system and statistical analysis on the number of strikes on the line electrode with different diameter was performed. The current flowing through the positive rod-line air gap was measured to obtain the charge current, and the integral of the charge current was calculated to evaluate the amount of space charge. The influence of space charge on the electric field in the vicinity of the line electrode was explored through the ANSYS. Experimental results showed that shielding effect of space charge on discharge strike point is significant under positive switching impulse voltage, but under negative switching impulse voltage, this shielding effect is not a leading factor influencing strike number and discharge path. The shielding effect of space charge is related with the size of line electrode. The larger the line electrode diameter is, the smaller the shielding effect of space charge becomes.