Modeling of Grounding Grids under Lightning Currents Using a Nonuniform Transmission Line Approach

Modeling a grounding system in the time domain makes it possible to account for the nonlinear phenomenon of soil ionization, which occurs following the injection of a very high-intensity lightning current. Several numerical studies using the Finite-Difference Time-Domain (FDTD) method have focused on modeling grounding systems while considering soil ionization. These works, which have produced excellent agreement with experimental measurements, directly solve Maxwell’s equations in three dimensions (3D), but they remain computationally intensive and numerically complex. In this paper, we propose a model for a grounding grid that offers a simplified implementation while accounting for the various electromagnetic couplings that arise after spatial discretization of the grid, as well as for soil ionization caused by the injection of a high-intensity lightning pulse. This new formulation is developed based on the equations of nonuniform Transmission Lines (nuTL) combined with the Finite-Difference Time-Domain (FDTD) method.