FDTD-based computational model applied to assess the influence of the frequency dependence of soil parameters on the lightning response of grounding electrodes for typical parameters of first and subsequent return stroke currents

This paper considers an evaluation of the influence of the frequency-dependence of soil parameters on the lightning response of horizontal grounding electrodes by means of the finite-difference time domain (FDTD) electromagnetic model. The FDTD simulations assumed the soil modeled as a multipole Debye medium and the response of grounding electrodes due to lightning return stroke currents with typical front time parameters of negative first and subsequent strokes was assessed. The results in terms of the ground potential rise (GPR) and grounding impulse impedance (ZP), were compared to those provided by the application of the Hybrid Electromagnetic Model (HEM), a frequency domain model widely applied for lightning related problems, and revealed the top quality of the modeled approach in FDTD. The largest percentage variations of the calculated impulse impedance compared to HEM were around 6 % and 10 % for first and subsequent stroke currents, respectively.