Voltage Stability Interface Limits in Non-Uniform Geomagnetic Disturbances

Geomagnetic disturbances (GMD) are rare events that threaten grid reliability, where the severity of the impact is highly uncertain. Transformer saturation caused by geomagneti-cally induced currents (GICs) produce an excess of reactive power loading, capable of decreasing voltage magnitude. Furthermore, traditional interface flow limits regarding voltage stability can become obsolete during a GMD due to these increases. Real time GMD-informed voltage stability limits would provide system operators with valuable information to help with mitigation of extreme solar storm effects. In this paper, the set of possible electric field permutations is searched to find a lower bound on interface stability limits with respect to a base operating condition. The interface limits are discussed as a function of the maximum electric field magnitude produced by a solar storm of a given strength. Numerical analysis techniques are utilized to identify an upper bound on interface flow limits that preserve voltage stability.