The impact of ground losses on estimations of lightning-induced voltage with dispersive soil parameters

In areas with frequent lightning activity, studying lightning induced voltage on overhead distribution lines is crucial to improve the line performance under nearby lightning strikes. This article studies the impact of ground losses in the transmission line model on lighting-induced voltage using an analytical approach. The soil characteristics was represented using fixed and frequency dependent soil models. Firstly, the lightning electromagnetic fields have been computed considering the influence of finite ground conductivity using Cooray-Rubinstein model. Afterwards, the lightning-induced voltage has been computed using Agrawal coupling model in frequency domain. The results show that incorporating ground losses in the transmission line model has a considerable effect on lightning-induced voltages at different velocities. The influence of velocity was evaluated at: 40 m/μs, 120 m/μs, and 200 m/μs respectively. It was found that the influence of ground losses on the peak value of LIVs is more significant at 40 m/μs. Since the median value of lightning velocities is 120 m/μs, it is deduced that the influence of ground losses is more pronounced at lower velocities as it causes an increase in the magnitude of lightning-induced voltage. The effect of incorporating ground losses in the transmission line model on lightning-induced voltage is also evaluated at various values of transmission line height. The effect of transmission line height was examined at 6 m and 10 m respectively. It was found that the effect of ground losses is greater at the height of 10 m at the midpoint of the transmission line. Consequently, as the height of the transmission line decreases, the influence of ground losses also decreases. However, the opposite occurs at positions far from the midpoint, where the influence of ground losses increases with lower transmission line heights. The impact of incorporating ground losses in the transmission line model on lightning-induced voltage is examined at different distances between the lightning channel and the transmission line. The effect of these distances was examined at values of 50 m and 100 m respectively. It was found that the influence of ground losses diminishes at distances of 100 m and above. Furthermore, lightning induced voltage magnitude with frequency dependent soil model is lower than with fixed soil model.