On-Load Network De-Icer Specification for a Large Transmission Network

This paper presents a feasibility study conducted with a view to installing an on-load network de-icer (ONDI) for de-icing HV transmission lines forming part of the Matapedia subtransmission network operated by Hydro-Quebec. The ONDI concept makes use of a phase-shifting transformer (PST) to induce very large ac currents to heat line conductors by the joule effect. A single ONDI can handle a number of lines of different length with no need to transfer loads to other lines or disconnect them. In the study presented, more than 900 km of 230- and 315-kV HV circuits can be de-iced with one ONDI installed at Rimouski substation. To put the ONDI to work, only existing circuit breakers need to be operated so that no open-air (ice-sensitive) disconnecting switches are involved. The adequacy of this planning study is also discussed here with regard to taking into account uncertainties related to the weather conditions expected for severe ice storms.