Geomagnetically induced current sensitivity to assumed substation grounding resistance

This paper considers the sensitivity of the calculated geomagnetically induced currents (GICs) in an electrical power system model to the assumed substation grounding resistances. Substation grounding resistances are not contained in standard power system models, and approximate values are often used in GIC studies. The paper provides an algorithm to quantify the degree of dependence of the GICs at any given substation. Case study results using the 20-bus GIC test system and a model of the North American Eastern Interconnect indicate that the substation GICs can be quite dependent on the assumed substation grounding values.