Ice detector estimation of atmospheric icing on a cable

Abstract

Atmospheric icing is an important cause of damages to structures and power transmission lines in northern Quebec. An icing test line was set up on Mt. Valin (alt. 902 m) near Chicoutimi to measure icing loads on the type of stranded cables used on transmission lines. Measurements of icing loads on a 100 m span stranded cable are obtained from the cable end tension. An ice detector which counts icing detection alarm cycles per unit time is used to estimate the icing intensity. Wind speed, direction and temperature at the study site were also recorded. A detailed study of a few icing events was made in order to relate the icing rate, as estimated by the ice detector, with the cable icing rate averaged in time from the load measurements. Two types of icing events can be distinguished from the range of the ice detector data. Freezing precipitation is associated with significantly higher icing intensities than cases in which only in-cloud icing occurs. Different calibration curves for icing rates of the ice detector were developed to predict cable icing for these two types of events. The cable icing rate is derived by taking into consideration the accretion size, wind direction and collection efficiency. Results indicate, that in most events, the ice detector data can be used to estimate ice loads on transmission line cables with an average per-hour error of 0.033 kg/mh. Estimations are generally more accurate at lower icing rates.