操作冲击下正极性长间隙放电物理仿真模型

A Physical Model to Simulate Long Air Gap Discharge at Positive Switching Impulse Voltage

开展正极性长空气间隙放电过程物理仿真模型的研究对优化特高压外绝缘设计具有重要的意义。基于正极性长间隙放电物理机制,建立了包括初始电晕起始与流注发展、先导起始、流注–先导体系发展和最后跃变等过程的物理仿真模型,该模型考虑了电晕起始分散性和先导路径随机性特征。采用有限元软件计算了放电结构间隙的背景电位分布,并使用试验观测结果对本文建立的模型进行了验证,最后采用该模型对导线–塔窗结构间隙的放电特性进行了仿真计算。结果表明:导线–塔窗间隙的50%击穿电压处于棒–板和棒–棒的50%击穿电压之间;波前时间对其50%击穿电压有比较明显的影响,呈现"U"形曲线;杆塔塔窗宽度对50%击穿电压影响较小,随着宽度增大,50%击穿电压有减小的趋势。

Researches on the physical model of long air gap discharge under positive impulse are of great importance for the well design of the ultra-high voltage external insulation. In this paper, based on the mechanism of the positive spark in long air gaps, a physical model including the process of the first corona initiation and the streamer development, leader inception, the streamer-leader system propagation and final jump was proposed. The statistical delay of the first corona inception and the random behavior of the leader advancement were taken into account in the proposed model. Moreover, a commercial finite element soft was applied to compute the background potential distributions for the all kinds of typical configurations. The model was validated with experimental measures and a good agreement was obtained. The discharge characteristics of conductor-tower window air gap under switching impulse voltage were simulated by using the proposed model in this paper. It was concluded that the 50% breakdown voltage for the conductor-tower window configuration is between the rod-plane＇s and the rod-rod＇s, and the wave time front has a relatively strong influence on the 50% breakdown voltage, which presents a ＂U＂ like curve. Furthermore, 50% breakdown voltage is slightly affected by the parameter of the tower window width, and the 50% breakdown voltage appears high as the tower window width becomes narrow.