A power-electronics-based transmission line de-icing system

Ice accumulation on transmission lines can cause extensive damage to the lines and towers, as demonstrated during the ice storm of January 1998, which caused serious damage power systems in Eastern North America. The Canadian province of Quebec was worst affected, with over a million consumers losing their electricity supply for some period. To avoid a recurrence of such a situation, Hydro-Quebec TransEnergie is investing in a dedicated power electronic "de-icer" installation. The HVDC-based installation, located at the strategically important Levis substation, near Quebec city, will inject a high direct current into a selected transmission line in order to melt the ice on it. However, operation in this mode is expected to be very infrequent. In the normal situation when the installation is not being used as a de-icer, it operates as a static VAr compensator (SVC), using the HVDC valves as a thyristor controlled reactor (TCR). An innovative main circuit design is used, minimising the power losses of the valves in SVC mode. The principal ratings of the de-icer installation in both de-icer and SVC modes are described in the paper, along with descriptions of the principal equipments and the circuit topologies used in the two modes.