基于山区雷电先导发展的改进电气几何模型仿真研究

Simulation Research of Improved Electro-geometric Model Based on Lightning Leader Development in Mountainous Terrain

山地对地面电场的畸变作用使雷电先导偏向山体发展,导致采用电气几何模型(EGM)计算的山区线路绕击跳闸率比运行经验偏小。因而提出一种适用于山区地形的输电线路雷击概率计算模型,通过一种类山体形态的保角变换函数将2维山区地形抽象化、映射到水平面,以使用传统镜像电荷法计算山区雷电下行先导的发展轨迹,并在先导"末跃"阶段采用电气几何模型EGM中的"击距"参数简化判断雷击点。仿真结果表明,应用该方法计算三峡地区几种典型山体地形的落雷分布,与雷电定位统计值具有良好的对应性。以三峡地区某220 kV线路雷击跳闸为例,与EGM计算结果对比表明,考虑山顶地形对雷电先导的吸引作用后,线路边相导线的绕击概率明显增大,可更好解释山区线路雷击跳闸率较高的原因。

The development of lightning leader is certainly attracted by the mountain terrain for electric field distortion affection, resulting in the shielding failure flashover probability calculated through EGM （electro-geometric model） to be smaller than the actual experience. Consequently, we put forward a novel computational model for lightning flashover probability in mountain terrain. Using a conformal mapping function to map the 2D mountainous terrain to the horizontal plane, the traditional image charge method was used to calculate the development track of lightning downward leader. Then, the parameter of striking-distance in EGM was adopted to simplify the lightning strike point in the lightning lead- er＇s last-jump. The simulation results show that the lightning distribution in some typical mountain terrain performs good agreement with the lightning location statistics in Three Gorges area. Compared with the results calculated through EGM model, the shielding failure flashover probability of the edge phase of a 220 kV transmission line in Three Gorges area increases significantly through the new model which considers the attraction effects on the lightning leader of mountain terrain. Therefore, the higher lighting flashover probability in mountain terrain can be well explained by the model.