Response of Grounding Electrodes to Impulsive Currents: An Experimental Evaluation

Abstract

Experimental results for the transient behavior of grounding electrodes are presented to clarify fundamental aspects of the grounding response to lightning currents. It is shown that for fast current waves, the value of impulsive grounding impedance <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ZP</i> of short electrodes is smaller than its low-frequency resistance <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LF</sub> while electrodes longer than the effective length have a resistance value smaller than impulsive impedance. The values found for the ratio <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ZP</i> / <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LF</sub> in the experiments are lower than those resulting from numerical simulation for electrodes shorter than the effective length.