Fast and Accurate Time-Domain simulation of Lightning Response in Grounding systems Considering Frequency-Dependent Soil parameters and Ionization

It has been demonstrated that most pole-residue sets proposed in the literature to represent the Alipio–Visacro (AV) model—which accounts for the frequency dependence of soil parameters using rational functions—result in high computational cost, making time-domain simulations inefficient for larger or more complex grounding systems. This inefficiency arises from the need for an extremely small time step in such simulations. Furthermore, it has been shown that an unnecessarily high precision requirement during wide-bandwidth curve fitting contributes significantly to the small time-step size. Since the ionization behavior must be updated at each time step, the computational burden becomes even more severe. To address this issue, a new set of poles and residues has been introduced for the AV model to represent the frequency dependence of soil parameters in time-domain simulations. This new parameter set significantly reduces computational costs while maintaining a level of accuracy comparable to that of previous models. Additionally, handling certain ionization-related calculations through lookup tables or predefined curves further reduces simulation runtime when soil ionization is considered. The effectiveness of this method has been validated through comparisons with the reliable frequency-domain Hybrid Electromagnetic Model (HEM).