Power transmission

Substation construction


There are nine main steps to build a substation to lower the voltage generated by transmission lines, and it takes many tradespeople to meet the challenge. At each step, we adopt strict safety, project quality and environmental protection practices.

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Aerial view of Judith-Jasmin substation. This type of substation receives electricity of up to 735 kV from transmission lines.

1. Establish the work zone

Before carrying out any work, it is important to establish the work zone and fence it off to ensure the safety of the access points.

Then, notices of work and site tags are installed to keep citizens informed throughout the construction period. In addition, other sources of information — including a Web page, an Info-project line, project news bulletins and press releases — are generally available to citizens, who may also contact the project's community relations advisor.

Throughout the project, site supervisors ensure that all the actions undertaken meet environmental, health and safety and quality standards.

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The work zone must be fenced off to secure the area.

A community relations advisor is assigned to every major project. Different communication tools are used to meet project needs.

2. Prepare the substation site

At this step, any trees growing in the work zone are cut down.

Then, the ground is levelled and earthwork is carried out.

The construction team prepares the work site by carefully setting aside the topsoil, which will be reused.

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Ground levelled to build Judith-Jasmin (2016) substation.

3. Excavate and lay the foundations

At this step, workers excavate the site, build the formwork, install the reinforcements and pour the concrete.

In addition to laying the foundations, we build all the underground concrete structures, such as the recovery basin.

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Excavation work at Fleury substation.

Building the foundations that will support the substation’s framework and equipment.

A basin is built around the foundations of the transformers to recover any oil in case of a spill.

4. Install the grounding grid

The grounding grid is installed to ensure the safety of people and the equipment. Buried underground, the grid redirects the fault current.

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Grounding grid: the metal wires that make up the grid will be buried.

5. Build the command building

As its name suggests, the command building houses the control and protection equipment.

Most substations are automated and remotely controlled. Only the largest substations have permanent technical staff on site since most are maintained by mobile teams.

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At public meetings, 3D renderings give citizens a better idea of the future command building.

The building houses the command and protection equipment.

A technician installs equipment in a circuit breaker panel.

Once the substation is operational, data is recorded and transmitted to the telecontrol centre.

6. Backfill the foundations and substation yard

Once the foundations have been laid, we backfill them and level the yard with granular material (sand, gravel, rock, etc.) that is adapted to the site.

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Backfilling the yard at Outardes substation.

7. Assemble the steel structures

Once the concrete is set, steel structures are assembled to support the electrical equipment. Other structures will support the control building.

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Specialized workers assemble the steel structures.

At Mont-Tremblant substation (2009), it took over 25,500 bolts to assemble the steel structures. The steel structures have an estimated total weight of over 13,000 kg.

8. Install the electrical equipment

Once the framework is built, we install the equipment on the foundations and steel structures.

For more information on the different types of equipment, click on the following links.

Each piece of equipment is then connected to the control room, which is under construction.

We permanently fence off the new installations to ensure everyone's safety. Our technicians test the equipment before the installations are connected to the power grid. Finally, we commission the substation and ensure that the electricity is flowing.

Follow the link to find out How a substation works and learn more about the different types of equipment that are installed.

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Power transformer at Saint-Bruno-de-Montarville substation (2013).

Power transformers convert high-voltage electricity into lower voltages for distribution.

Transformers are very heavy. For example, at Baie-Saint-Paul substation (2016), each transformer weighs 80 tonnes: almost as much as 55 cars.

9. Landscape and carry out the final inspection

The project ends with landscaping: we plant trees, create mounds of earth and do more work if necessary.

We do earthwork, demobilize the site and carry out the final inspection to wrap up the project. Only the operating equipment is left at the substation.

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In this rendering (2016) of the future 315/25-kV Saint-Patrick substation, trees help create a visual screen.

Landscaping on the site ensures that the substation is seamlessly integrated into the environment.

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