A Marching-on-in-Time Method of Moments for Computation of Transient Potential Rise of Grounding Grids Exposed to Lightning Strikes

The article proposes an efficient full-wave electromagnetic method to compute the value of the ground potential rise for a grounding system exposed to the first and subsequent lightning strokes. The grounding system consists of a grid of several vertical and horizontal electrodes (with no constraints on the number of electrodes) buried in a lossy soil. The proposed method adopts a time-domain (TD) numerical method based on the method of moments (MoM) and marching-on-in-time to solve the governing TD electric field integral equation. This is done by expanding the unknown currents along the conductor in terms of a finite linear combination of products of appropriate spatial and temporal basis functions. Using the Galerkin method in space and the point matching method in time leads to a recursive computation of the current both in space and time. Compared to its rival frequency-domain MoM (FD-MoM) modeling, the proposed method is found to be computationally much more efficient as no matrix filling or inversion is required for a large number of frequencies. The efficiency of the proposed method is demonstrated by comparing the simulation results of several case studies with those obtained using the conventional FD-MoM modeling.