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.