Discover Hydro-Québec TransÉnergie and its system
Features of Our Transmission System

Normally, it is very costly to transmit large quantities of electricity reliably over very long distances. Energy losses inevitably occur, and the risks of disturbances and equipment failures are high. The greater the distance, the harder it is to maintain a constant voltage when demand fluctuates. This distance factor has led Hydro-Québec TransÉnergie to develop a variety of techniques designed to use a minimum of equipment while maximizing continuity of service.

• 735-kV lines
  One of these innovations was the 735-kV line. In 1965, Hydro-Québec became the world's first utility to commission a line at such a high voltage.
• Series compensation
  Series compensation, a capacitor-based technology, changes the electrical behavior of transmission lines, causing them to act as if they were shorter. The lines are strengthened this way and can therefore carry greater amounts of energy. The flexibility inherent in this solution offers major gains, as the construction of more lines can be avoided and additional power brought onto the grid more easily. For better voltage control, Hydro-Québec TransÉnergie also uses shunt compensation, as well as synchronous and static compensators, allowing reactive power to be generated or absorbed.
• Direct-current power transmission
  Another specialty of Hydro-Québec TransÉnergie is direct-current (DC) power transmission, used to facilitate the transmission of large quantities of power over long distances at high voltages (e.g., 450 kV). This technique allows interchanges with neighboring grids, as power can be transferred between two asynchronous alternating-current (AC) systems. This is the case with Hydro-Québec TransÉnergie's multiterminal DC system (MDCS), for example. The MDCS link includes the world's first converter substation of its kind. This link begins by transmitting direct current some 1,200 km from James Bay to Nicolet substation, in the heart of the inhabited part of Québec. Nicolet substation also receives alternating current from the Manic-Outardes complex and Churchill Falls generating station in Labrador. In addition to helping meet the demand of several large urban centres, this energy hub is used to export and import electricity, because of its ability to transform AC into DC and then back to AC.

A reliable system
Hydro-Québec TransÉnergie has a stringent maintenance program to ensure the reliability and efficiency of its facilities and the security of its system control. By refining its maintenance planning processes, the division is also able to reduce equipment outage time. With superior reliability a top priority, Hydro-Québec TransÉnergie offers customers service quality and a continuity index that are among the best in the world.

A system on the leading edge of technology
To improve the performance of its system, Hydro-Québec TransÉnergie devotes several million dollars every year to developing and adapting technological innovations. Click here to see some examples