Cable rime accretion measurements on a Laurentian mountain

Rime is an important cause of damage to structures in northern Quebec, Canada, and a major concern about the reliability of power transmission lines. An atmospheric icing test line was set up at Mt. Valin (altitude 902 m), near Chicoutimi, to measure icing rates on stranded cables. Two cables, the first one 96.5 m (316.5 ft) in span and the second one 32.6 m (106.9 ft), were used to investigate transmission line icing by comparing icing, for a complete winter, on two stranded cables, 35 mm (1.38 in.) in diameter for the first cable and 8 mm (0.315 in.) for the second. Measurements taken during the 1986–1987 winter season are analyzed. Ice accretion and shedding are correlated with ice detector alarms and wind velocity respectively. The icing intensity, considered to be proportional to the number of icing alarms per unit time, is strongly correlated with the cable icing rate. A significant correlation is also verified between the wind velocity and the ice shedding. Results of this investigation indicate that wind velocity and icing detector alarm rate are important variables to predict total ice mass on cables exposed to winter in-cloud icing. With more similar data, the implementation of an empirical icing model to estimate cable icing in mountain ranges will become possible. Key words: transmission line icing, rime accretion, ice shedding.