Under high impulse currents, an earthing system exhibits different impulse characteristics depending on the shape and/or design configuration of the earthing system. These characteristics have been seen to be different with respect to its steady-state as highlighted in many studies. Furthermore, in order to ascertain that a correct design of an electrical system is achieved, it is important to evaluate the impulse characteristics of the earthing system under high impulse conditions. So far little emphasis has been given in previous publications to investigate the characteristics of earthing systems under high impulse conditions by field measurements. For this reason, a rather efficient and reliable technique to solve this problem is by conducting a practical analysis (field experiment). This paper investigates the characteristics of a single rod electrode under high impulse conditions by field measurements under different polarities. The single rod is selected in this paper for its simple configuration and installation. It was observed in this study that the resistance of the single rod earthing system was seen to reduce with increasing current magnitudes for both polarities and negative polarity has higher impulse resitance than that of positive polarity.

This paper investigates the effects of current magnitudes, steady-stage earth resistances, R-DC, and threshold electric field, E-c on the characteristics of earthing systems under impulse conditions by using Finite Element Method (FEM). It has been reported in literature that there are three scenarios that can occur when the earthing systems are subjected under high impulse conditions as compared to its steady-state conditions, namely; (i) no difference in its resistance values between steady-state and impulse conditions, (ii) earth resistances under impulse were found to be lower than that at steady-state, and (iii) earth resistances were found to be higher under impulse than that at steady-state. It was found that the largest reduction in impulse resistance occurred for the earth resistance with the highest values for different factors; current magnitudes and Ec. Crown Copyright (C) 2014 Published by Elsevier Ltd. All rights reserved.