Geomagnetically induced currents (GIC)

Ground effects of space weather are generally known as GIC (geomagnetically induced currents). GIC are driven by the geoelectric field associated with a magnetic disturbance in electric power transmission grids, pipelines, communication cables and railway equipment. Sketch about the creation of GIC.

When flowing through transformers, the dc-like GIC may cause saturation leading an increase of the exciting current. Several problems may then arise: an increase of harmonics, unnecessary relay trippings, an increase in reactive power losses, voltage drops, a black-out of the whole system, permanent damage to transformers.

When flowing from the pipeline into the soil, GIC may increase corrosion of the pipeline, and the voltages associated with GIC disturb the cathodic protection system and standard control surveys of the pipeline.

The most famous GIC failure occurred in the Canadian Hydro-Quebec system during a great magnetic storm on March 13, 1989. The system suffered from a nine-hour black-out.

The Finnish Meteorological Institute (FMI) has been active in powerline/pipeline oriented GIC research for over twenty years. Methods for the calculation of a geomagnetically induced electric field have been constructed, and methods for the calculation of the actual GIC in power systems and pipelines have been developed and tested within projects with the Finnish power/pipeline industry. GIC measurements have been important part of these projects, and there are at the moment continuous measurements of both, GIC in the Finnish pipeline and GIC in the Finnish power system (see sections: GIC in pipelines and GIC in powerlines).

FMI participated to the international Space Weather Month campaign (September 1999) organized by SCOSTEP/S-RAMP. During the campaign, Nordic GIC data from several sources were collected to the database at FMI. Quicklook plots of data can be found from this site.