Impact of lightning channel base current (CBC) function modelling on computed lightning induced overvoltage waveshapes

Adverse effects of lightning strike are studied through the modeling of the lightning-induced over-voltage (LIOV) using the channel base current (CBC) functions. A lightning current is characterized by the parameters like current peak value (Im), time-taken by the current to reach Im (tm), maximum rise rate of the lightning current (di/dt)max (steepness), and charge transferred at the point of contact of the lightning strike (Q). Using the CBC functions, the lightning electromagnetic fields (LEMFs) are calculated to compute the LIOV using a coupling model. Since the choice of CBC function plays an important role in LIOV computation, the present work studies its effect on the computed LIOV. As a preliminary study two functions: Heidler’s and NCBC functions were examined. It was shown that the a-sort-of delay characteristic from the NCBC function is reflected in the computed LIOV and also the tripolar nature of the LIOV for the case imperfect ground.