Assessment of lightning current parameters suitable for analysis of HV substation overvoltage protection

This paper will present theoretical and mathematical background of the process which aims at evaluation of lightning current parameters suitable for the analysis of high voltage transformer station overvoltage protection. It is a well appreciated fact that the analysis of overvoltage protection for the high voltage substation stems from the backflashover analysis on several first neighboring towers of the incoming overhead transmission line. Statistical distribution of lightning current parameters is employed in the process of deriving analytical expression which expresses a probability of lightning current with specific parameters (striking several first towers as seen from the substation) being exceeded only once during the specified time frame. A typical numerical example will corroborate the analysis with concrete results.