Electromagnetic Field Due to Lightning Strike to a Tall Tower Sitting on a Mountainous Terrain

This paper presents the results of a radiated electromagnetic field due to lightning strike to a tall tower sitting on a mountainous terrain when considering both the first and subsequent return strokes. A cone-shaped ground with finite conductivity represents the mountainous terrain; and a cylindrical two-dimensional finite-difference time-domain (FDTD) scheme is used to determine the lightning-generated electromagnetic fields. The return stroke channel is modeled using the antenna theory model with fixed inductive loading which is appropriately incorporated into the FDTD algorithm. Simulation results are presented for different values of the cone angle and height, and for different values of the tower height. It is shown that when the first and subsequent return strokes hit a tower on a cone-shaped ground, the radiated electric and magnetic fields experience an enhancement in their amplitudes as compared to the case where the tower sits on a flat ground. Also, the current reflections from the tower base, influencing the current distribution along the tower and radiated electromagnetic field waveforms, depend on the cone angle and height, as well as the tower height.