Load-Flow Studies in the Presence of Geomagnetically-Induced Currents

Large transient fluctuations in the earth´s magnetic field can produce quasi-dc currents in electric power systems. These geomagnetically-induced currents (GIC´s) cause half-cycle saturation in power transformers resulting in increased transformer var requirements. This paper discusses the phenomena by which GIC´s are produced in power systems, the system and transformer modeling necessary for representing the effects, and the results of load-flow studies made with GIC present in a large interconnected power system in the northern United States and Canada. Results of the studies are compared with data recorded during a geomagnetic storm.