Underground Cable Systems Ground Return Impedance Sensitivity to Soil Resistivity Uncertainties

The soil characterization of an underground cables installation may be poorly known and present a wide variation throughout the year. This represents a challenge when it comes to an accurate evaluation of transient overvoltages/currents and the correct assessment of voltage and current profiles throughout the circuit. This paper presents a discussion based on a sensitivity analysis for the ground return impedance of underground cables systems to soil resistivity, which is typically considered as a deterministic parameter. For the evaluation of the impact of uncertainties we have considered the analysis of the most common configuration in cable systems. A frequency domain analysis was carried out to assess the actual impact of the uncertainties in terminal voltage and currents. Results indicate that the usage of sensitivity might provide a helpful insight in the impact on the overall system performance with respect to soil resistivity uncertainties.