Current and voltage distribution in a horizontal earth electrode under impulse conditions

In this paper, the behaviour of a horizontal electrode under impulse conditions is investigated experimentally at the Cardiff University outdoor earthing test facility. The test electrode consists of 88.5 m long copper conductor buried to a depth of 30 cm, and is divided into sections with test pits located along the electrode to enable access for voltage and current measurements along its length. A test circuit is established using an auxiliary current electrode, and a low voltage impulse generator is used to inject current of different magnitudes and shapes into the test electrode. The effect of current injection location, electrode length and current rise time is quantified on the current and earth potential rise (EPR) distribution along the electrode. The measured voltage and current signals were analysed at various points on the electrode to determine the effective length. Good agreement between measured and computed values was obtained. Based on an analysis of the results, the effective length of a horizontal electrode under the particular test conditions was determined and good agreement between measured and computed values was obtained.