Electric potential assessment near distribution power lines caused by lightning surge wave propagation

Lightning surge propagation either to overhead or underground power line generates transient faults, which give rise to electromagnetic perturbations within power networks and other utilities. Limitation of lightning surge effect remains an important task for both designers and researchers. This paper deals with the analysis of the effect of lightning surge propagation near tower structures of overhead power lines through underground networks, within voltage range of 20 kV. The research was performed based on Finite Element Method as a time domain simulation of 45 μs. The lightning current flows within a discharge channel with different lengths (15-91 m) and impedances, according various peak values (2.5-40 kA). For the lightning current modeling the 8/20 μs wave shape was applied, particularly for each peak current. It was evaluated around tower structure of power line and near underground power network, the electric potential dependency by lightning current, soil resistivity and installation depth of underground power cables. It is concluded that the effect of lightning surge propagation through underground power cables is strongly dependent by the voltage working range of the underground network and by his own parameters like length and peak current flow. The results obtained by this work give an assessment of the effect of lightning surge propagation from near tower structure of overhead power lines through underground networks within medium voltage range.