Research of Lightning Leader Development in Mountainous Terrain Based on Conformai Mapping

The operating experience of power system suggests that the development of mountain lightning leader is certainly attracted by the mountain terrain for electric field distortion affection, resulting in increased CG lightning density in transmission line corridor area. This paper presents a simulation model applicable to lightning strike probability of transmission lines on abstract mountainous terrain. By a conformal mapping function, which has a similar shape as mountain, the abstracted 2D mountainous terrain will be mapped to the horizontal plane, then the image method is used to calculate electrical-potential field and Development Track of the lightning downward leader on mountainous terrain by LPM (leader progression model). The Striking Distance of EGM (electro-geometric model) is adopted as an important parameter to simply determine lightning strike point on lightning lead'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 mountainous terrain 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.