Improvements Related with the Measurements of Substation Grounding Grid Resistance Applying Auxiliary Probes at a Short Distance: Theoretical Analysis

This paper deals with improvements related to the application of the Fall-of-Potential Method to measure the substation grounding grid parameters considering short distances between the grounding system under test and the auxiliary current electrode. The improvements are related to: (a) use of material with low resistivity value around the auxiliary current electrode to increase the current between this electrode and the earth electrode system under test; (b) proof that the measured potentials (touch and step) is conservative (in favor of safety) due to the coupling effect between electrodes and (c) obtain a curve and an expression that allows to determine the position in which the potential electrode should be placed to estimate the grounding grid resistance of the substation under test.