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Hydro-Québec TransÉnergie
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Features of Our Power System

* Distance is the mother of invention
* Series compensation breakthroughs
* System operations–Linking the supply chain
* Telecommunications
* A highly automated system
* Superior service all the way down the line
* The Québec control area

Distance is the mother of invention

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 longer the distance, the harder it is to maintain a constant voltage when demand varies. This distance factor led Hydro-Québec TransÉnergie to develop a variety of techniques using a minimum of equipment while maximizing the continuity of supply.

One of these innovations was the 735-kV line. In 1965, Hydro-Québec became the first utility in the world to commission a line at such a high voltage. True to its commitment to constantly improve the system, Hydro-Québec TransÉnergie reinforced its high-voltage transmission lines by installing series compensation at strategic points from 1989 on.

Series compensation breakthroughs

Series compensation, a capacitor-based technology, changes the electrical behavior of transmission lines, causing them to act as if they were shorter. The lines become more stable and can convey greater amounts of energy. The flexibility inherent in this solution leads to 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.

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 enables interchanges with neighboring grids; power can be transferred between two asynchronous alternating-current (AC) systems.

This is notably the case with its multiterminal DC system (MDCS). Hydro-Québec TransÉnergie's MDCS link includes the first converter substation of its kind in the world. This link begins by transmitting direct current along some 1,200 km between James Bay and 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. An energy hub, Nicolet substation plays an important role in securing the power supply. In addition to helping meet the demand of several large urban centres, the substation is used to export and import electricity due to its ability to transform AC into DC and then back to AC.

System operations
Linking the supply chain

All activities related to power system management are the responsibility of the System Control Branch, whose mission it is to balance power grid supply and demand in real time throughout the transmission system under its jurisdiction, and in keeping with power quality expectations and regulations set by the electricity industry.

With its multidisciplinary team, the System Control Branch steers the generation and transmission of electricity, as well as its delivery and receipt through the various interconnections. At the System Control Centre in Montréal, over 140 experts (scheduling, guidelines and procedures, real-time control and computer technology) work to maintain the supply-demand balance and system integrity at all times. Their decision-making weighs several factors, including predicted demand, weather forecasts, planned outages and reliability criteria.

Aside from its obligation to keep the power grid stable in real time, the mandate of System Control mandate encompasses security coordination for the Québec Control Area. By complying with strict reliability standards established by organizations such as the North American Electric Reliability Council (NERC) and the Northeast Power Coordinating Council (NPCC), Hydro-Québec is positioned to take advantage of the opening North American bulk power transmission market.


Telecommunications are crucial for monitoring generation and transmission facilities, as well as for system operations and maintenance. The development of generating stations in remote northern regions has led Hydro-Québec to build its own telecom network—the largest private network in North America. It supports the transmission of large amounts of data to the regional operating centres and to the main System Control Centre in Montréal in order to ensure remote protection of lines and apparatus, remote control of generating stations and substations, power dispatching and telephone communications. Other circuits are reserved for wireline telephony, mobile communications, Internet services, etc.

A highly automated system

Because we have to transmit electricity over long distances and under difficult weather conditions, which increases the risk of disturbances, Hydro-Québec TransÉnergie has developed highly effective special protection systems. These systems maximize transmission capacity and ensure power system stability.

  • Load frequency controllers (LFCs) continually adjust the balance between electricity demand and output.
  • Automatic switching systems for shunt reactors (called "MAIS") help restore the system voltage profile to 735 kV following a disturbance.
  • The generation rejection and remote load-shedding (GRRL) system, the world's most extensive, detects disturbances and acts almost instantly—within a few hundredths of a second—to prevent a major blackout.
  • Remote undervoltage load shedding (RULS) protects the system against the risk of a voltage collapse following the loss of lines in peak periods.

Superior service right down the line

Day after day, our employees strive to improve service by making the system more accessible and efficient. We have a stringent maintenance program to ensure the reliability and efficiency of our facilities and the security of our System Control Centre. By refining maintenance planning processes, we're able to reduce equipment outage time.

Even the risk of geomagnetic storms is not taken lightly; after a system-wide power failure due to an intense solar storm in March 1989, Hydro-Québec TransÉnergie reviewed its protection equipment and introduced specific operating strategies that made a later storm of similar intensity a non-event. Such accomplishments, and many others, demonstrate the multidisciplinary expertise that keeps the utility's continuity index among the best in the world.

The Québec Control Area
Responsibilities related to the Northeast Power Coordinating Council (NPCC)

The Northeast Power Coordinating Council (NPCC), one of 10 regional bodies belonging to the North American Electric Reliability Council (NERC), consists of several control areas that oversee system security and bulk energy transfers in their respective territories.

Every area is responsible for managing generation and transmission facilities, conducting exchanges with neighboring systems, and respecting NPCC reliability criteria as well as NERC policies.

Hydro-Québec TransÉnergie is in charge of the Québec Control Area, wich includes Labrador and the Alcan and Maclaren power systems.

To guarantee the reliability and efficiency of interconnected systems, the NPCC has established policies and guidelines for planning, operations and maintenance

In spite of the challenges posed by great distances, our system fully complies with the criteria of the NPCC, which governs transmission providers in the Northeastern United States and Eastern Canada.

This compliance with NPCC criteria lifts TransÉnergie's export restrictions affecting interconnections of approximately 250 to 500 megawatts, thus offering more reliable service for our customers in Québec and beyond our borders.

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