The Evolution of Québec Earth Models Used to Model Geomagnetically Induced Currents

Geomagnetically induced currents (GIC) in power systems can interfere with the system operation and, in extreme cases, can damage transformers and cause power blackouts. A notable example is the magnetic disturbance of March 13, 1989 that caused a blackout of the Hydro-Québec system. The size of the GIC depends on the inducing magnetic-field variations, earth conductivity structure, and system characteristics. This paper examines the earth models developed for Québec and shows how the changes in earth models have changed the electric-field values calculated for the March 13, 1989 storm. These calculations are made using data from two magnetic observatories: one at the southern end of Québec and one at the northern end. It is shown how the choice of magnetic-field data and uncertainty in the earth model influence the calculated electric-field values.