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  Geographic location
  The James Bay territory
  Access infrastructures
  The Robert-Bourassa hydroelectric development
  The dam
  The dikes
  The spillway
  The spillway deck
  The reservoir
  The intake and the headrace
  The underground facilities
  The machine hall
  The scrollcase
  The generating units
  The surge chamber
  The tailrace tunnels
  The control room
  Radisson village
  Radisson substation
  The James Bay transmission system


Image : The James Bay Transmission System

Because of its extensive system, Hydro-Québec has been a world leader in power transmission for a long time. Hydro-Québec commissioned the world's first 735-kV line in 1965. Never before had such a high voltage been used to transmit electricity. In 2001, this breakthrough was named the technological innovation of the 20th century.

Since the electricity is generated far from load centres, it must be transmitted over long distances.

This is the role of Hydro-Québec's transmission system, or grid. And the system is very extensive. Five lines transmit the power generated at Churchill Falls and at the Manic Outardes complex. Five other lines carry the output from Phase I of the La Grande complex. The eleventh line is the multiterminal direct-current link.

A twelfth line carries the electricity generated by Laforge-1, Laforge-2 and Brisay generating stations, built during Phase II of the La Grande complex.

Erection of the five transmission lines for La Grande Phase I required 12,500 towers, 60,000 km of conductors and 10,000 km of ground wire. In addition, 13 switching stations had to be built. In all, the system cost $3.1 billion, that is, more than 25% of the total cost of La Grande Phase I.

Transmission lines

Each transmission line has three bundles of conductors, one for each phase of current. Each bundle is composed of four conductors kept at equal distance by spacers. Each conductor consists of 48 strands of aluminum twisted around a steel core 1.25 cm in diameter. The steel gives the conductor mechanical strength and the aluminum gives it electric conductivity.

The tops of all the towers are connected by two wires. These are the ground wires, which act as a kind of surge arrestor to protect the line. The electric field in the conductors induces a current in the ground wires, and Hydro-Québec uses this induced current to supply the telecommunications stations close to the lines. The technology for extracting induced currents in ground wires was exported to Peru to supply small mountain villages located close to transmission lines.

Towers

Because there are so many transmission lines, there is also a variety of towers. Some tower designs reflect the specific function of the tower, while others have come about as a result of technological progress.

The role of some towers is to support the conductors along straight stretches of line. When the first high-voltage lines were run from the Manic-Outardes complex to the load centres, very massive self-supporting towers were used. These towers require an average of 21 tonnes of steel for each kilometre of line. Hydro-Québec researchers then developed the guyed-V tower, which requires only 11.8 tonnes of steel per kilometre of line, on average.



While the James Bay transmission system was being built, a technological breakthrough was made. The cross-rope suspension tower was developed, a tower that requires an average of only 6.3 tonnes of steel per kilometre of line. This is why three of the five transmission lines are supported by guyed-V towers, while the other two are supported by cross-rope suspension towers—so called because of the steel cable between the tower limbs that replaces the rigid crossbar of the earlier models.

Angle structures, which Hydro-Québec's imaginative linemen have nicknamed "penguins," are used to change line direction.


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