On HF Circuit Models of Horizontal Grounding Electrodes

Inductance to ground in high-frequency circuit models of horizontal grounding electrodes is often ldquoerroneouslyrdquo approximated by applying image theory. Two other approximate approaches that are often used are based on a transverse electromagnetic propagation assumption and on a homogeneous medium assumption, respectively. We compare these three approaches with an ldquoexactrdquo electromagnetic approach by computing the grounding impedance in scenarios with soil resistivity of 10-1000 Omegamiddotm and electrode length up to 100 m. Surprisingly, the circuit model based on the image theory leads to better results in case of inductive behavior. This is also confirmed by comparison with experimental results.