Abstract-This paper presents a methodology for integrated power flow modeling of the impact of geomagnetic disturbances (GMDs) on the power system voltage stability. GMDs cause quasi-dc, geomagnetically induced currents (GICs) in the transformers and transmission lines, which in turn cause saturation of the high voltage transformers, greatly increasing their reactive power consumption. GICs can be calculated using standard power flow modeling parameters such as line resistance, augmented with several GIC specific fields including substation geographic coordinates and grounding resistance, transformer configuration, and transformer coil winding resistances. When exact values are not available estimated quantities can be used. By then integrating GIC into power flow analysis, the changes in reactive power losses and bus voltages can be quantified to assess the risk of voltage instability and large-scale voltage collapse. An example calculation is provided for a North American Eastern Interconnect model.

Geomagnetically induced currents (GICs) have the potential to severely disrupt power grid operations, and hence their impact needs to be assessed through planning studies. This paper presents a methodology for determining the sensitivity of the GICs calculated for individual and/or groups of transformers to the assumed quasi-dc electric fields on the transmission lines that induce the GICs. Example calculations are provided for two small systems and for the North American Eastern Interconnect model. Results indicate that transformer GICs are mostly due to the electric fields on nearby transmission lines, implying localized electric field models may be appropriate for such studies.

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Embedding the modeling and simulation of geomagnetically induced currents, GIC, into power flow simulation software allows the study of sensitivity and transient stability of the North American bulk power system under the distress of a geomagnetic storm. Modeling the interaction between the auroral electrojets and the Earth's atmosphere is a crucial step in determining the geoelectric field induced by the geomagnetic storm. Geomagnetic storms interact with the Earth's magnetic field, inducing damaging currents into the power grid, which have proven to be harmful to high voltage transformers and the overall stability of the power grid.