Abstract :
The paper describes a self-regulating heating element for preventing the formation of ice on an overhead transmission line. The device described is a 1:1 current transformer having a low-Curie-temperature-alloy core. Heat is generated by iron losses and by resistive losses in the single short-circuited secondary winding during freezing ambient conditions. The alloy core has a Curie temperature of +15°C. The theoretical design of a deicing element is proposed, based on the magnetic properties of a quarternary alloy of nickel, chromium, silicon and iron. Details of the heat required to prevent the formation of ice on a 0.175 in2 (equivalent copper section) steel-cored aluminium conductor are discussed, and the performance of a production prototype deicing element is compared with the design figures. The paper is concluded by a description of full-scale field trials which are currently taking place at the Lecht Pass in Northern Scotland.
