Earth Resistivity Measurements Using Cylindrical Electrodes at Short Spacings

The accuracy of power system grounding analysis is critically dependent on the resistivity of the local soil surrounding the grounding system. This paper develops and discusses a new closed-form formula based on field theory relating soil resistivity to measured resistance which relaxes the requirement that rod electrodes have a large spacing compared to their buried length. The paper also demonstrates that the interpretation of practical resistivity measurements based on the new equation is significantly more accurate than the one based on the classical equation.