Assessment of the Effects of the Electromagnetic Pulse on the Response of Overhead Distribution Lines to Direct Lightning Strikes

In the usual practice, the evaluation of overvoltages due to direct lightning strikes to overhead power lines is focused on the representation of the effects of the lightning current injection, whilst the effects of the coupling between the conductors and the lightning electromagnetic pulse (LEMP) is disregarded. Motivated by recent results obtained for the case of a medium voltage line configuration with a shield wire, this paper extends the analysis to assess the contribution of the LEMP on the lightning performance of an overhead distribution line with and without periodically grounded wires and surge arresters. Moreover, the paper deals with the LEMP effect on the occurrence probability of flashovers on different phases, which is an important information on the service continuity of networks with isolated or compensated neutral earthing. A validation of the results is obtained by comparing the overvoltages calculated by the electromagnetic transient program including the model of the line illuminated by the LEMP and those obtained by a three-dimensional finite difference time-domain approach.