The presented results are related to the application of extreme value theory to assess the level of impacts from extreme space weather events on a technology of critical importance: to electric power transmission. The extreme value theory has been applied to more than 4 solar cycles (1973-2018) of geomagnetic data recorded at Canadian geomagnetic observatories to provide an estimation for one in 100 years magnetic storm. This analysis has been done separately for the periods related to the solar minimum and the solar maximum, presenting the influence of the solar cycle variations on extreme value estimations. The developed method has been also applied to evaluate the geoelectric fields induced by geomagnetic activity and affecting transmission power lines for different location across Canada.