A series capacitor rated at 108 Mvar is in operation in the 230 kV power transmission grid of Hydro-Québec at Des Hêtres 230/120/69 kV substation in Québec, Canada. The series capacitor, supplied by ABB as a turnkey commitment, has the task of increasing the power transmission capacity over an existing inter-connector bringing power from several hydro power plants down to the consumer areas.
The Rapide-Blanc to Des Hêtres inter-connector is 145 km long and consists of a single circuit 230 kV line. Its initial power transmission capacity was exceeded as new hydro power generating facilities were going on line upstream, and more than 150 MVA of additional hydro power needed to be transmitted down to Des Hêtres. In this situation, series compensating the existing line came as an attractive option to the traditional solution of building a new, parallel 230 kV line, or upgrading the existing line to a higher voltage.