On the Influence of Stroke Current Propagation Velocity on Lightning Horizontal Electric Fields (original) (raw)

2000, IEEE Transactions on Electromagnetic Compatibility

This paper discusses the influence of stroke current propagation velocity on the characteristics of lightning horizontal electric fields, considering different types of soil and distances to the stroke location. The MTLE model is adopted for the determination of the current distribution along the return stroke channel, whereas the effect of the finite-ground conductivity is taken into account by using the modified Cooray-Rubinstein approximation. This paper also discusses the effect of the propagation velocity on each of the horizontal electric field components. The results show that the horizontal electric field is strongly influenced by the stroke current propagation velocity even for the case of good conductive ground and observation points relatively close to the stroke location. Regardless of the ground conductivity, the peak value of the static component decreases and the negative peak of the radiation component increases with the propagation velocity. Therefore, for short distances to the lightning channel, the absolute peak value of the horizontal electric field tends to decrease as the velocity increases, while for distances of few kilometers or larger its behavior is just the opposite, i.e., the amplitude increases with the propagation velocity. Index Terms-Electromagnetic fields, electromagnetic transient analysis, electromagnetic transient propagation, lightning, timedomain analysis. I. INTRODUCTION A LARGE number of problems on overhead power distribution lines are related to overvoltages induced by indirect strokes. Such overvoltages depend on the lightning-radiated electromagnetic fields, which by their turn are strongly affected by various parameters. Lightning electromagnetic fields propagate over a finitely conducting ground and the various frequency components are attenuated to different degrees. The horizontal electric field, in particular, is strongly affected by the ground conductivity and its effect on the characteristics of lightninginduced voltages on overhead lines can be significant. Thus, in order to better evaluate the lightning performance of power lines and design more effective protection systems, it is important to understand how the horizontal electric fields are affected by the lightning and ground parameters.