Statistical methods for evaluating lightning induced effects on distribution lines (benchmarking, methodology, the induction model importance)

Summary form only given. Lightning induce voltages have been seriously reconsidered by power utilities and researchers due to the increasing demand of good quality by customers in power supply. The contribution reviews the standard procedures to evaluate the flashover rate vs basic insulation level (BIL) curves (IEEE 1410 Guide-Distribution Lightning Performance) and describes another methodology used to estimate such curves by means of a statistical program based on the Monte Carlo method for the evaluation of the lightning performances of distribution lines. The program provides the number of lightning events that exceed, for a certain ground flash density, a given value which, in turn, allows estimation of the frequency distribution of lightning-induced voltages for a given line, as well as the flashover rate vs. BIL curves. The computation of the induced voltages is performed using the LIOV code (lightning induced over-voltage), developed within the framework of an international research collaboration involving the University of Bologna Department of Electrical Engineering, the Swiss Federal Institute of Technology (Power Systems Laboratory) and the University of Rome “La Sapienza” (Department of Electrical Engineering). The influence of the main parameters of interest is examined (ground resistivity, lightning current peak amplitude and rise time, return-stroke velocity) along with the influence of the various critical distance expressions used in the analysis