Determination of earth resistance of multiple driven-rod electrodes

In the paper a new method is presented for the determination of the earth resistance of a single-rod electrode, based on the concept that the equipotential surfaces around the electrode are similar in shape to the electrode itself. The resulting analysis for the potential field is then extended to evaluate the earth resistance of multiple-driven-rod-electrode systems, by applying the method of superposition. The analysis brings out the fact that, for the experimental determination of the earth resistance by the usual fall of potential method, the current electrode need not be kept at a large distance from the earth electrode. A modification of the normally adopted method is suggested, and, to facilitate the work of the field engineer, a normalised curve for the accurate determination of the earth resistance is presented. To test the validity of the analysis, extensive experiments have been conducted in the field, as well as using an electrolytic tank. The close agreement obtained between the test results and the analytically computed values for all these cases, as well as for the data available in the literature, is thought to provide substantial evidence in support of the basic assumption.