On the Lightning Electromagnetic Fields due to Channel with Variable Return Stroke Velocity

M Izadi,M Z A Ab Kadir,M Hajikhani

doi:10.1155/2015/150756

Abstract

Numerical field expressions are proposed to evaluate the electromagnetic fields due to the lightning channel with variable values of return stroke velocity. Previous calculation methods generally use an average value for the return stroke velocity along a lightning channel. The proposed method can support different velocity profiles along a lightning channel in addition to the widely used channel-base current functions and also the general form of the engineering current models directly in the time domain without the need to apply any extra conversions. Moreover, a sample of the measured lightning current is used to validate the proposed method while the velocity profile is simulated by the general velocity function. The simulated fields based on constant and variable values of velocity are compared to the corresponding measured fields. The results show that the simulated fields based on the proposed method are in good agreement with the corresponding measured fields.

Highlights

Lightning is an important natural phenomenon that can affect power lines
Induced voltages are a major effect of lightning on distribution lines that can be created by coupling between the electromagnetic fields of the lightning and the power line [1,2,3,4,5]
Among the different channel parameters, the return stroke velocity is an important variable for the evaluation of lightning electromagnetic fields [10, 12, 13], and this is usually entered into field calculations as an average value of velocities at different heights along a lightning channel, with a typical value between c/3 and 2c/3 (c is speed of light in free space) [14]

Summary

Introduction

Lightning is an important natural phenomenon that can affect power lines. Induced voltages are a major effect of lightning on distribution lines that can be created by coupling between the electromagnetic fields of the lightning and the power line [1,2,3,4,5]. Among the different channel parameters, the return stroke velocity is an important variable for the evaluation of lightning electromagnetic fields [10, 12, 13], and this is usually entered into field calculations as an average value of velocities at different heights along a lightning channel, with a typical value between c/3 and 2c/3 (c is speed of light in free space) [14]. Numerical field expressions are proposed to evaluate lightning electromagnetic fields based on a channel with variable values of return stroke velocity directly in the time domain. The proposed method is applied to a typical current sample whereby the corresponding return stroke velocity function is used for considering the velocity profile along a lightning channel.

Return Stroke Current

The Return Stroke Velocity

The Proposed Electromagnetic Field Expressions

Conclusion