Potential Probe Position in Ground Resistance Measurement of Horizontal Electrodes in Multi-Layers Ground by the Fall-of-Potential Method

Abstract

A difficult problem is encountered when the ground resistance of a large grounding system is measured by the fall-of-potential method. The problem is that a horizontal curve section does not exist with a fall-of-potential curve. In this case it is difficult to estimate the ground resistanse from the fall-of-potential curve.
In this paper, a method for determination of potential probe position to estimate the ground resistance of horizontal electrodes (counterpoise and mesh), is proposed when the horizontal curve section does not exist. First the exact potential probe position is obtained in two-layers ground case. Second, in three-layers ground case, three-layers ground is replaced with two-layers ground by some procedures, and the potential probe position for the three-layers ground is taken as the position for the replaced two-layers ground. Error extent of the ground resistance from the replacement is estimated. Third in four-layers ground case, the procedures for replacement of four-layers ground with two-layers ground are described, and error extent of the ground resistance from the replacement is estimated also in this case. Last, for the case where the ground configuration is not clear, another method is proposed and error extent is described.