In late January, the sun hurled billions of tons of plasma at up to 5 million mph toward Earth, which produced a dazzling light display in northern regions of the world. Radiation from the explosion made the 93-million-mile trip to Earth within 34 hours after the solar explosion. The event put the nation's utilities on alert for possible disruption of the power grid

The Electric Power Research Institute (EPRI) measures geomagnetically induced currents (GIC) through its SUNBURST program, a system of strategically positioned monitoring sites throughout the United States and Canada. It uses data from that system to provide guidance to utilities on keeping the power-delivery system functioning during solar storms and to provide feedback to those developing GIC models and forecasting tools. In the future, models of the power system, designed to evaluate the flow of GIC could be included to enhance the capability of the system.

The SUNBURST monitoring system recorded minor levels of GIC beginning at approximately 15:04 UT (10:04 a.m. EST) on Jan. 24, 2012. This was the result of a solar flare that erupted early on Jan. 23. During this event, only one SUNBURST site in the EPRI measurement system exceeded 10 A of dc current on the neutral, and did so for less than one minute (GICs are quasi-dc and can cause saturation of transformer windings if the levels are high enough and last for extended periods; currents less than 10 A are generally considered to be low risk for causing transformer problems). Low-level GICs were measured at most other SUNBURST sites.

The largest dc currents generally coincided with the onset of the event. Most of the GIC activity occurred between 15:04 UT (10:04 a.m. EST) and approximately 18:00 UT (1:00 p.m. EST) on Jan. 24. Activity continued through Jan. 25 but at much lower levels. Some sites recorded neutral dc currents that approached 5 A twice during the first half of Jan. 25.

EPRI is working with NERC and the utility industry to develop, among other things, the capability for utilities to assess the impact of an extreme geomagnetic disturbance on the grid.

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Utility Neutral current level
Central Hudson - Pleasant Valley -5.2 A to 8.6 A
Central Hudson - Hurley Avenue -6.2 A to 5.5 A
Central Main Power/Bangor Hydro Electric - Chester -6.5 A to 5.5 A
Manitoba Hydro - Grand Rapids -9.1 A to 9.7 A
Con Edison of New York - Goethals -9.4 A to 4.7 A
Tennessee Valleu Authority - Paradise -25.0 A to 11.1 A
National Grid Company US - New Scotland -2.7 A to 1.5 A

Note: List only includes sites that experiences significant GIC levels.