Effect of the Surface Impedance on the Induced Voltages in Overhead Lines From Nearby Lightning

摘要

This paper presents the calculation results of lightning-induced voltages on overhead lines using two different formulations for the horizontal electric field at the earth surface. The first one is a time-domain equation equivalent to the surface impedance contained in the Cooray–Rubinstein formula, while the second one is an improved equation that provides more accurate results in the vicinity of lightning. The induced voltages are calculated for a strike in the vicinity of the line (50 m) and the results show that, for good-conducting earth, the two formulations are equivalent. However, for poor-conducting earth, the second expression provides a higher and longer induced voltage. Based on the calculation results, a limiting condition for the use of these equations is proposed.