On the Behaviour of Vertical Ground Electrodes under High Frequency Currents

This paper aims to study and analyse the behaviour of ground electrodes at low and high frequency ranges. Single-layer soil is considered where several values of soil resistivity are selected. Elaborating CDEGS code, simulations are carried out to determine the grounding impedance over frequency up to ten megahertz. A parametric analysis is conducted for a better understanding of the system behaviour. From the obtained results, it is found that the low-frequency impedance is directly proportional to the soil resistivity, and inversely proportional to the electrode length. At high frequency, the capacitive behaviour of the grounding systems increases with soil resistivity while inductive behaviour is proportional to the electrode length. Oscillatory behaviour can also be obtained at very high frequencies, and the Z/R ratio and Nyquist impedance plots are proposed to facilitate the understanding of the system behaviour. The results indicate that the proposed curves are helpful practices to easily understand and discuss the behaviour of grounding electrodes.