Projected changes to extreme ice loads for overhead transmission lines across Canada

Ice accretion on transmission lines can lead to serious damages from line breakage and flashover. This study investigates projected changes to design ice loads for overhead transmission lines for the 2041-2070 and 2071-2100 periods with respect to the 1976-2005 period over Canada, using transient climate change simulations of the fifth generation Canadian Regional Climate Model, for two driving Global Climate Models and two Representative Concentration Pathways. Projected changes to freezing rain characteristics are first evaluated and results suggest decreases in 50-year return levels of annual maximum daily freezing rain for the south-eastern inland and coastal regions and south-western and north-eastern coastal regions of North America, but increases for other regions. Consequently, the simulations suggest statistically significant increases in 50-year return levels of annual maximum ice thickness, particularly for regions of Quebec and west of the Hudson Bay (larger than 10 mm) and some scattered increases for south- central and western Canada (mostly smaller than 3 mm). This study also helped identify regions where both wind and ice loads will increase in future climate, which can be detrimental to the electric infrastructure. Results suggest that compound event assessments would be valuable, taking into consideration larger set of simulations, to obtain more robust projections.