Maximum Limit of Allowable Ground Potential Rise of Substation Grounding System

Substation grounding systems should guarantee the safety of equipment and human beings. This paper discusses the maximum ground potential rise (GPR) of substation grounding systems resulting from short-circuit ground faults, the potential difference on the insulations of secondary cables and devices, and the relationship between the potential difference on the insulation of substation secondary systems and the GPR. The safe parameters of grounding systems should include touch voltage, step voltage, and GPR. For an actual layout of a grounding grid and secondary cables in a respective actual soil model, the maximum core-sheath potential difference on the insulations of secondary systems can be analyzed if it is set as k% of GPR. Since the experimental results of the minimum power-frequency withstand voltage of the insulations of secondary systems is higher than 2 kV, 200/k kV is suggested as the maximum limit of allowable GPR of substation systems. For the extreme case, k% is smaller than 40%, and 5 kV is determined as the maximum allowable value of GPR under the shielding sheath of secondary cables grounded in both terminals.