FDTD analysis of distribution line voltages induced by non-vertical lightning

摘要

This paper investigates lightning induced over-voltages on overhead lines considering "bent" and "computationally-generated" non-vertical lightning channels by using a finite-difference time-domain (FDTD) method. In the former case, combinations of vertical and inclined channels with different connecting heights are modeled to represent "bent" lightning. It is made clear that the peak voltage is significantly influenced by the lightning channel geometry under 100-m altitude when severe conditions of a 1/200-mu s current and a lightning distance of 50 m are assumed. Induced voltages on the three-phase line show similar characteristics to those on the single conductor line. In the latter case, a lightning-like (zig-zag) channel is computationally generated by a probabilistic calculation based on an electric potential distribution in a three-dimensional space, and its induced voltage is compared with that by a simply-inclined channel. When average inclined angles under 100-m altitude in the computed channel are set to the angles for a simply inclined channel, the induced voltages show good agreement. The difference is less than 10% and it decreases as the earth resistivity increases. These results indicate that realistic non-vertical lightning can be represented by simply-inclined lightning by considering average inclined angles in low altitude.