A method for the assessment of the indirect lightning performance of distribution networks

The paper presents a general procedure for the evaluation of the indirect lightning performance of a distribution network, which takes into account the actual network topology and the presence of transformers, surge arresters and line poles. The procedure is an extension of a Monte Carlo-based approach developed for a single straight overhead line to the case of a more complex distribution network consisting of a number of lines (main feeder and laterals) and typical power components. The procedure is based on the accurate evaluation of the induced voltages along the network, achieved by using the LIOV-EMTP computer code, which combines a model for the calculation of lightning-induced overvoltages (LIOV) on overhead lines with the electromagnetic transient program (EMTP). In order to reduce the required computational effort, a heuristic technique is proposed and its accuracy is verified. Finally, the paper presents a comparison between the lightning performances of distribution networks characterized by the same overall length of overhead lines but with different topologies. The effects of the presence of line poles, transformers and surge arresters are also analysed.