Study of geoelectromagnetic disturbances in Quebec, 1. General results

With the aim to better understand the flow of geomagnetically induced currents in the power system and to be able to prevent GIC inconveniences in the future, Hydro-Quebec carried out measurements of the geoelectromagnetic field in Quebec at five sites, spread over 250 km, from 1992 to 1994. This included magnetometers and the use of 25 km long phone cables to measure the electric field. The largest disturbances were found to occur when the auroral electrojet moved close to the recording sites. The magnetic disturbances varied little over the five sites, but the electric fields varied greatly from site to site due to changes in the local geology. An analysis: of events with electric fields E greater than or equal to 1 V/km found an approximate linear relationship between E and horizontal dB/dt. The directions of these electric fields were roughly east-west, consistent with the electrojet as the cause of the disturbances.