Finite-difference modeling of dispersive soils validated via experimental evaluation of transient grounding signals

In this paper, we develop a soil dispersion model into the FDTD algorithm for analyzing grounding systems. The model is constructed by inserting into frequency-domain Maxwell-Ampere equation a Padé approximant for σ+jωε, in such way functions available in literature describing the frequency dependence of soil's parameters are properly represented. With adequate mathematical manipulations, time-domain equations for uptating electric field are obtained. The second contribution of this paper is the design and construction of a low-cost surge generator, which is used in the experiments as the voltage excitation source. The results show that the simulated signals are in excellent accordance with measurements.