The calculation formulas for various types of earth grounding systems (EGR) have been determined by considering them as a single entity; consequently, the specific components of length and cross-section of the dispersion resistances are not distinctly identified within the calculation structures already proposed in standards and regulations. In many situations, however, which deviate from the idealized assumptions regarding the soil-conductor considered when establishing the calculation formulas for the dispersion resistances of EGR, the cross-sections and even the lengths of these resistances could be estimated with sufficient precision to determine the dispersion resistance values. Thus, the contact surface between the metallic parts-consisting of electrodes and EGR connecting conductors—could constitute a calculation basis for the ground conductor cross-section; it must be determined how this cross-section behaves when the current through the EGR traverses the soil (which possesses a different resistivity than the electrodes and connecting conductors) along a path that should remain as close to the surface as possible due to the skin effect, while bypassing any insulating obstructions along the way. The question “what is the path of the fault current through the soil?” arises, immediately followed by another regarding the role of the operational and protective EGR. This paper supports, through explanations, arguments, formulas, and numerical results, the evaluation of EGR dispersion resistances by distinctly determining their length and cross-section. This is proposed as a method for sizing EGR when conventional methodologies do not yield results that align with measurements taken at completed sites
Bentea et al. (Thu,) studied this question.