Rebuilding of the 69‑kV transmission line between Cap‑aux‑Meules and Grosse‑Île

The current line dates back to 1980 and is sometimes subjected to extreme weather conditions that can impact its useful life. A number of steps have therefore been taken to extend its service life. The rebuilding will secure the supply of electricity to the archipelago with a new line designed to current standards that takes into account the specific environmental conditions of the region, such as high winds, freezing rain, salt air and shoreline erosion.

The new line will meet current construction standards, and the solution selected will be adapted to the archipelago’s specific environmental conditions. However, outages may still occur, even with a new line in place, especially because of extreme weather events that occur in the region. Hydro-Québec makes every effort to ensure service continuity but isn’t spared from harsh climate conditions.

Several scenarios will be assessed during the draft-design stage. Technical, financial, environment and social considerations will be examined as part of the analysis.

The draft-design stage for reconstruction of the line began in summer 2021, therefore the outages of the following winter are unrelated. However, the project team has been informed of the outages and will take them into account in the draft-design studies.

Hydro‑Québec is dedicated to providing our customers with a robust and reliable grid, and one way we do this is through a preventive maintenance program. However, the specific environment of the islands presents a variety of challenges for our equipment (for example, numerous storms, strong winds, salt air and erosion).

Hydro‑Québec is aware that outages were more frequent than usual in Îles-de-la-Madeleine during winter 2021‑2022. We quickly deployed teams and mobilized resources to assess the status of the equipment and the grid to determine the cause of the outages. All data collected was analyzed, and an appropriate intervention strategy was implemented for both the distribution and transmission systems.

The distribution line between Cap-aux-Meules and Grosse-Île substations is a redundancy (like a safety line) that ensures system reliability. In the event of an outage affecting the transmission system, for example, the line might have to be de-energized for safety reasons while repair work is carried out. During the work, the distribution line takes over to provide electricity to customers. Therefore, if the transmission and distribution lines were installed on the same structures, service continuity could not be provided.

Service interruptions on the transmission system will be required at certain stages as the line is being rebuilt. However, almost all customers will be supplied by the distribution system by then. Situations where customers can’t be supplied by the distribution system will be carefully analyzed so we can determine the best solution in each case. Interruptions will be short and planned in advance to minimize inconvenience.

Erosion in Îles‑de‑la‑Madeleine is taken into account and documented by UQAR’s Laboratoire de dynamique et de gestion intégrée des zones côtières, a research group that collects data and provides projection modelling. Hydro‑Québec’s project team adds appropriate safety factors to these projections to ensure that the solution selected for rebuilding the line doesn’t amplify erosion.

The sensitive elements are well identified and limited in scope. Many of them can be avoided by selecting an appropriate route and design concept adapted to the specific context (for example, through thoughtfully established overhead and underground portions). However, we can rarely avoid all sensitive elements in power line projects. Mitigation and/or compensation measures help reduce the residual impacts on sensitive elements to an acceptable level.

The chosen environmental assessment method used by Hydro‑Québec for power line projects includes a detailed landscape study. The goal of this study is to characterize the various types of landscapes in the study area to determine which are the most sensitive to a line crossing.

Specific consideration is given to valued landscapes in line route planning. The small size of the territory and the project’s technical complexity, however, leave few alternative route options