GEOMAGNETICALLY INDUCED CURRENTS IN THE FINNISH HIGH-VOLTAGE POWER-SYSTEM - A GEOPHYSICAL REVIEW

We consider geomagnetically induced currents (GICs) in power systems f rom the viewpoint of a geophysicist. Special attention is paid to the Finnish high-voltage power system, in which exact theoretical model ca lculations together with recordings have been performed for several ye ars. We present several examples of theoretically computed GICs using different geophysical models for estimating the geoelectric field driv ing GICs. Statistical prediction of GICs is outlined referring to stud ies made in Finland. We show that a combination of GIC recordings at f ew sites with theoretical modelling of ionospheric currents and the ea rth's conductivity, and data of geomagnetic activity makes it possible to derive GIC statistics of the entire power system. Finally, we disc uss requirements for a long-range prediction of GICs, which will obvio usly be a widely-studied topic in future.