A geomagnetic disturbance (GMD) can result in severe damage to the power grid by inducing quasi-dc currents called geomagnetically induced current (GIC). Protection against GMD therefore necessitates the accurate estimation of GICs. GICs estimation is challenging because it depends on substation grounding resistances, which 1) depend more on the local soil and earth conditions than the construction of the substations themselves and 2) can vary by more than an order of magnitude, from 0.05 to 1.5 ohms. Substation grounding resistances are not contained in standard power system models, and approximate values are often used in GIC studies. This motivates the study in this thesis, which proposes a method to calculate the sensitivity of GIC at any substation due to both the substation being studied and neighboring substations’ grounding resistances. The work provides an algorithm to quantify the degree of dependence of the GICs at any given substation. The effectiveness of the method is illustrated using parameters from a real world power system. The 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 local substation grounding values. Subsequently, the same systems were studied to include neighboring substation grounding resistances. Although a few cases were dependent on the neighboring values, the local substation grounding resistances were more significant overall. These methods and results are further discussed and analyzed in this work.
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Geomagnetically induced current sensitivity to assumed substation grounding resistances in the power system
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