Power Transmission
Building a Line
Background
There are seven main steps to build a transmission line and it takes many tradespeople to meet the challenge. At each step, Hydro-Québec adopts strict safety, project quality and environmental protection practices. For example, it is environmentally sound to build in winter since construction on frozen ground considerably reduces certain impacts.
Video: Building a 735-kV line: Quebec has met the challenge
Duration: 1 minute 47 seconds
Building a power transmission line is a major challenge that involves seven major stages and a wide diversity of skilled workers. In this video, you'll witness the stages to building a transmission line carrying 735 kV: the highest level of voltage in Hydro-Québec's network.
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Safety, the environment and quality are top priorities at all times.
Conventional towers-also called lattice towers‐are the most common type in
Québec.
Guyed V towers are very light and often built in areas that are difficult to
access.
Tubular towers are more easily integrated into certain environments and are
often installed in urban areas.Stages
1. Transporting materials to the tower sites
The materials are transported to each tower site.
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The parts are carefully distributed and the construction materials needed for
each tower are left directly on the site where the tower will be built.
2. Building the foundations and anchors
The construction team begins by clearing the project area. The workers carefully set aside the topsoil, which will be reused. During excavation for the foundations that will stabilize the tower, pumping may be required to remove the water and dry the site. The size of the excavation site depends on the type of soil and the type of tower. Anchors depend on the type of tower installed.
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Concrete foundations are poured for self-supporting and tubular towers.
Steel-lattice foundations (in overburden) are used for guyed and self-supporting
towers. They are the most common type of foundation.
Pile foundations with ground anchors are built when the soil’s load
bearing capacity is too low (clay or silt).
Guy anchoring adapted to V towers
3. Assembling the towers
The project area must be adapted to the type of tower that will be built. Because this step requires the use of heavy machinery, all the necessary precautions are taken. For example, in wetlands, steel plates are sometimes placed on the ground to accommodate the machinery and preserve the environment.
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Line workers assemble the towers on the ground. This step may seem simple enough
but a tower is actually a huge 3D puzzle that requires a lot of experience and
skill to put together. 
4. Raising the towers
Once the tower is assembled on the ground, it is raised using a telescopic crane.
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The raising of a tower in the Matapédia region.
5. Unreeling and installing the conductors
The conductors are unreeled and strung section by section from tower to tower. There is a cable drum with a reel and tensioner at one end and a puller and take-up reel at the other. In this step, workers make sure that the voltage levels in the conductors are within acceptable limits and that there is adequate clearance between the ground and the cables. Our practices are adapted to account for sensitive and special environments.
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Tension site, equipped with a drum and tensioner, and pull site, equipped with a
puller.
Using specialized equipment, we bring cable reels, also called drums, directly
to the jobsite. These drums hold 2 to 3 km of cables. 
Here, electric cables are laid on wooden planks to avoid damaging them during
pulling.
To reduce inconveniences, including traffic disruptions, cables are sometimes
pulled at night in urban settings.
6. Installing the counterpoise wires
Counterpoise wires are installed to ground each tower and protect the line from lightning. A counterpoise wire is actually an underground conductor that ensures the electrical connection between some or all of the line’s towers and the ground.
When minor excavation and filling work is required, mitigation measures are implemented. For example, counterpoise wires are not installed near wetlands to avoid heavy machinery traffic and excavation.
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A bulldozer equipped with a reel at the front and a ripper at the back is used
to install the counterpoise wires. It has extra-wide tracks to exert less
pressure on the ground.
The ripper is equipped with one to three blades to dig deep into compact soil to
place the counterpoise wires.
7. Restoring the site
Once a project is complete, Hydro-Québec always restores the site by:
- removing all the debris and waste
- levelling the ground
- dismantling the temporary accesses (roads, bridges, culverts)
- repairing any infrastructure that was damaged during the work (roads, fences, etc.)
- seeding or planting whenever necessary based on the characteristics of the site (shoreline, wetland, etc.)
When the work is carried out on private land, Hydro-Québec meets with the landowners to ensure they are satisfied with the restoration. It takes responsibility for any damages that may have occurred as part of the work and compensates the landowners according to project regulations.
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1. During construction
2. The site restoration after one year
Final state of the site of the 315-kV supply line for Anne-Hébert
substation
Final state of the site of the 230-kV Saint-Césaire‐Bedford line on
agricultural land
