An Application of HVDC to the de-icing of Transmission Lines

Ice accumulation on transmission lines in extreme climatic events can result in severe damage to the lines and towers, with the possibility of being unable to restore the service quickly enough to preserve electricity supplies to customers. To prevent such a situation, Hydro-Quebec TransEnergie are investing in a dedicated "De-icer" installation at its strategically important Levis substation, near Quebec city. The HVDC-based installation, scheduled for handover in August 2006, injects a high direct current into the transmission line to be de-iced. When not being used as a de-icer, the installation operates as a static var compensator (SVC), using the HVDC valves as a thyristor controlled reactor (TCR) in a circuit which minimises the power losses of the valves. The detailed function of the de-icer installation is described in the paper, along with descriptions of the principal equipments and the circuit topologies used in the two modes