Modelling and Simulation of Lightning Electromagnetic Fields Using an Hybrid Method for Poorly Conducting Ground Case

The aim of this paper is the calculation of lightning electromagnetic fields for a poorly conducting ground. For this objective, we first, discuss the return stroke models in two categories: Transmission line (TL) models and Travelling-Current Source (TCS) models. Usually, the representative expression of engineering models doesn’t include two of the TCS models which are the Diendorfer and Uman (DU) model and Modified DU with additional Decay (MDUD); for that, a new expression is proposed in this paper which solves this problem. Secondly, use is made of a hybrid technique based partially on the quasi- image theory, for the calculation of magnetic field, and on a Finite Difference Time Domain (F.D.T.D.) method, for the calculation of electric field components, taking into account the finite conductivity of the ground. The results are compared with other approximate numerical methods available in the literature. Our approach reproduces the same wave shapes of the electric and magnetic fields above the ground of a finite conductivity. Nevertheless, some discrepancies can be observed which can be explained by the differences in the lightning current model and current parameters.