Author(s): Jacques Druez; Pierre Mccomber
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Keywords: No Keywords
Abstract: A test line was set up at Mt. Valin (alt. 902 m) near Chicoutimi in Canada, to measure atmospheric icing. This line, 100 m in span, was designed and built in collaboration with Hydro-Quebec to investigate icing of power line conductors and insulators. The icing on two single stranded cables (12,5 and 35 mm in diameter), and a four conductor bundle are compared. Four strings of insulators, 3 m in length, are suspended between two beam supports on one of the two poles. They are respectively porcelain, glass, anti-fog and long-rod synthetic insulators. The end tension is measured by load cells in the cables and insulators. From these measurements an average ice load is calculated for each cable. Temperature, wind velocity magnitude and direction are also recorded. An icing detector signals the occurrence and duration of the icing events. Icing measurements are taken since the end of the 1985-86 winter. The most important icing events have been analyzed more closely to compare icing on various elements of the test line. From the present observations it can be concluded that the ground wire (12,5 mm in diameter), even if it is smaller, accretes more ice when compared with the larger conductor (35 mm in diameter). This appears to be related to its higher flexibility in torsion which tends to increase its twisting during icing. The larger single cable accumulates slightly less ice than one of the bundle cables of the same size. On the other hand, more ice shedding occurs along the bundle. During an icing event, the icing rate is fairly constant at least if no important shedding due to strong winds occurs. Ice shedding is not presently considered in ice accretion models for cables and it appears to be an important phenomenon for this particular type of flexible structure. Results for the insulators indicate that the synthetic insulator, smaller in size, accretes merely 25% of the ice collected on any of the three other types of insulators. However, for the more rigid long-rod insulator, the ice load over a longer time period reaches 60% of the accretion on any other tested insulator.
Year: 1988