The response grounding electrodes to lightning currents: the effect of frequency-dependent resistivity and permittivity of soil

A methodology to find the variation of soil resistivity ρ and permittivity ∈ in field conditions at the typical range of lightning-current frequencies was proposed and applied in low- and high-resistivity soils. Considering this variation in simulations using the hybrid electromagnetic model HEM was able to practically match results of theoretical and experimental voltage waves developed in response to the impression of impulsive currents with lightning-pattern waveforms to horizontal grounding electrodes buried in the analyzed soils, different from the results obtained with the conventional approach of constant values for ρ and ∈.

1 Introduction

In theoretical evaluations of the transient behavior of grounding related to lightning-protection applications, the value adopted for soil resistivity is usually the one measured by commercial instruments, which employ low frequency signals (~100 Hz). The value of relative soil permittivity is usually assumed between 4 and 80, according to the soil humidity [1].