Improving the reliability of power systems with more accurate grounding system resistance estimates

While there are standards and papers which specify in detail how to make soil resistivity measurements using the Wenner 4-pin method, nowhere is there any published reference indicating what range of pin spacings is required in order to obtain sufficient data for an adequate substation or power plant grounding grid design. This paper quantifies the degree of error that can occur in the computed grid resistance, touch voltages and step voltages as a function of maximum pin spacing, as the soil structure is varied through a wide range of values.