Research Article

Geomagnetically induced currents in Norway: the northernmost high-voltage power grid in the world

¹ Department of Physics, University of Helsinki, P.O. Box 64, 00014, Finland
² Finnish Meteorological Institute, Erik Palmenin aukio 1, 00560 Helsinki, Finland
³ Statnett, PB 4904 Nydalen, 0423 Oslo, Norway

^* Corresponding author: minna.myllys@helsinki.fi

Received: 23 September 2013
Accepted: 3 February 2014

Abstract

We have derived comprehensive statistics of geomagnetic activity for assessing the occurrence of geomagnetically induced currents (GIC) in the Norwegian high-voltage power grid. The statistical study is based on geomagnetic recordings in 1994–2011 from which the geoelectric field can be modelled and applied to a DC description of the power grid to estimate GIC. The largest GIC up to a few 100 A in the Norwegian grid occur most likely in its southern parts. This follows primarily from the structure of the grid favouring large GIC in the south. The magnetic field has its most rapid variations on the average in the north, but during extreme geomagnetic storms they reach comparable values in the south too. The ground conductivity has also smaller values in the south, which further increases the electric field there. Additionally to results in 1994–2011, we performed a preliminary estimation of a once per 100 year event for geoelectric field by extrapolating the statistics. We found that the largest geoelectric field value would be twice the maximum in 1994–2011. Such value was actually reached on 13–14 July 1982.