Probabilistic Assessment of Ground Potential Rise Using Finite Integration Technique

The behavior of grounding systems against waves with high-frequency content such as lightning or very fast transient overvoltages is completely different from the steady state. This paper presents a more flexible model of a grounding system with respect to frequency dependency of electrical parameters of soil and moisture variations using the finite integration technique (FIT). The applicability and accuracy of the FIT have been verified against experiments as well as conventional methods such as method of moments, finite-difference time-domain method, and partial element equivalent circuit. In addition, the impacts of moisture variations of soil on resistivity and permeability have been quantified through Weibull distributions. The obtained probabilistic parameters of soil resulting from moisture uncertainty have been involved in the model to provide a more realistic model. The probabilistic ground potential rise indicated that the grounding system can be optimized up to 50% by accepting a low rate of risk depending on the soil moisture level. The provided insight is a beneficial approach, especially for a gas insulation substation, where the available space is limited for a grounding system.