Modeling of lightning surges on a grounding system of a tower cascade

Propagation of electromagnetic lightning transients modeling in the electrical network is not an easy task because of the large dimensions of its various equipment (length of power lines and ground wires, height of towers horizontal ellipsis ). The full wave numerical methods well known in modeling, generally based on the mesh of the electromagnetic device to construct a system of equations, can prove to be cumbersome or even inapplicable to treat this problem. To study the lightning direct impact on a towers cascade equipped with its lines and earth connections, this article presents a realistic approach based on the transmission line equations. This new modeling, developed directly in the frequency domain, allows taking into account the frequency variations of the ground electrical characteristics in order to analyze properly the grounding systems transient behavior, particularly the Ground Power Rise during a back-flashover.