Resistance calculation of interconnected grounding electrodes

The calculation of earth resistances by the average potential method has proved to give accurate results. Various publications [1], [2] shows that current distribution in the electrode has little effect on the calculated result assuming uniform current distribution. The above method however, requires that integration be carried along the electrode path [1]. For complex interconnected grounding electrodes this introduces difficulties which usually have been avoided by taking adequate points (Representative points) on the electrode and averaging the potentials calculated for these points [2], [3], [4]. The average potential obtained is then considered to be the potential rise of the electrode. This however requires a judicious selection of points and/or a large number of points in order to obtain an accurate result. For large interconnected electrodes the consequence is large computing time or difficulties to chose adequate representative points specially when uniform current distribution in the electrode is assumed. This paper introduces a method which permits the integration to be carried along the path of an interconnected electrode buried in a two layer soil. The general formula for the earth resistance calculation is derived and applied to typical cases. The reader should note that the method is also applicable for the calculation of average potential values.