Impulse Efficiency of Grounding Electrodes: Effect of Frequency-Dependent Soil Parameters

The effect of frequency-dependent soil resistivity and permittivity on the lightning response of electrodes subjected to representative currents of first and subsequent strokes was analyzed. Expressions for expediting the estimate of the impulse impedance, effective length, and impulse coefficient from the measured low-frequency resistance and soil resistivity that take this frequency dependence into account were proposed for some electrode arrangements of practical interest. The estimates were shown to be consistent with the results simulated using an elaborate model and with experimental results.

I. Introduction

Grounding electrodes have relevant influence on the operation of electrical systems. In most cases, they provide a low-impedance path for dispersion of currents toward the soil and ensure a smooth distribution of the electrical potential developed on the ground surface in response to the flow of impressed currents.