• Highlights

    Upgrading infrastructure in a way never seen in the history of the transmission grid

    France’s transmission grid is one of the oldest in Europe (average age of about 50). Over the next 15 years, it will be critical to upgrade the existing network to ensure quality of electricity supply, and the pace of renewal will need to increase. The policy set forth in the Ten-Year Network Development Plan focuses on three priorities:

    • Maintain today’s average level of quality throughout the country;
    • Improve the “everyday network”;
    • Promote economic optimisation.

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    Replacing conductors

    A three-phase circuit has three phases, each using between one and four conductor cables to carry energy.
    There are currently close to 99,300 km of overhead lines, representing some 400,000 km of conductor cables.
    The type of conductor used depends in large part on when it was installed. There has been a gradual effort since the 1970s to replace the original ones, made of aluminium-steel, with other technologies, notably almelec (aluminium alloy, magnesium and silicon), which is currently used with nearly 65% of conductors.
    Conductors are considered to have an age limit of 85 years. This means that, starting in 2030, and in a structural manner over the following decades, replacement efforts will reach a pace never before seen in the history of the French power system.

    Age pyramid of overhead conductors


    15 km of power lines and 37 pylons removed from the landscape in Rive-De-Gier

    RTE completed the removal of a 63 kV overhead line in the commune of Rive-de-Gier (Loire), the last step in the network adaptation project begun mid-2018, at the request of the Saint Etienne metropolitan area. Work was completed during the summer with the commissioning of a new power line just 700 metres long, and the elimination of 15 km of lines and 37 pylons.

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    Upgrading power lines also means replacing pylons

    RTE maintains its infrastructure in such a way as to keep it in good condition over time, which in turns protects third parties and keeps the power system operating safely.
    Power lines are upgraded not only by replacing conductors but also by renovating and even replacing the pylons that are central to RTE’s mission.

    During the summer, 36 pylons on the 90 kV Anstaing – Orchies line were renovated or replaced to make the electricity network in the Lille region more secure.

    As part of its multiannual maintenance scheduling, RTE replaced 24 pylons on the Anstaing – Orchies line (90 kV). Twelve pylons were partially renovated (head or console, for instance). This project was done in several phases: assembly of the new pylon, disconnection of cables and dismantlement of the old pylon, lifting of the new one into place and reconnection of cables.

    Undergrounding of lines in the centre of the Oise

    As part of its renovation of the 63 kV power grid in the centre of the Oise, RTE has replaced a majority of the overhead cables with underground lines.
    This project was conducted in two phases: the northern section was completed and brought into service in 2018, between La Hérelle and Valescourt, and the southern section between Valescourt and Thiverny was completed in 2020.

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    Completion of the MESIL project in Montpellier

    The longest MESIL (Mise en Souterrain d’Initiative Locale – Undergrounding by Local Initiative) project in France was completed on 20 October 2020, in Montpellier. RTE conducted this exceptional project over several years in collaboration with metropolitan authorities.

    Four high-voltage cables, including two at 225 kV, were buried by RTE, allowing the old overhead lines to be taken down. With a total of 13 km of lines taken down and 36 pylons removed, the project has freed up land for economic activities that will support Montpellier’s development. It will also benefit those who live and work in the region by improving the quality of their urban environment and landscapes.

    The project represented an investment of €18.6 million, of which €13.6 million was financed by Montpellier Méditerranée Métropole.

    The next MESIL project will be completed in 2023. It will involve undergrounding five overhead power lines running through the towns of Clamart and Le Plessis-Robinson, in the Paris region.
    A total of 14 km of overhead lines will be taken down and 18 km of underground lines created, with security of supply to the area guaranteed throughout the project. In all, 54 km of power cables will be laid unground. Launched in 2017, this project will allow Clamart and Le Plessis-Robinson to realise their plans to enhance their attractiveness by building 350,000 sq m of new homes and 85,000 sq m of retail.

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    Start of work to prepare for the 2024 Olympic Games

    A major project now underway involves undergrounding four 225 kV power lines that currently run over the towns of Villeneuve-La-Garenne, Saint-Denis and Ile-Saint-Denis.

    By taking down 15.7 km of power lines and 27 pylons, RTE will free up more than 80 hectares of land just outside Paris. The towns are very much looking forward to a project that will allow them to execute their plans to build housing, retail, offices, and parks in Villeneuve-La-Garenne.
    Saint-Denis and Ile-Saint-Denis will use the freed-up space to build the Olympic Villages for the 2024 Games.

    The project will be conducted in three phases:

    • 2020: Completion of the entrance and exit pits for the tunnel boring equipment. The entrance pit, located rue Volta, in Saint-Denis, is currently under construction;
    • 2021: Boring of the 2.5 km tunnel;
    • 2022: Fitting out of the tunnel and connection of the new power line.

    The next step will be to remove the pylons and overhead lines, a process that will start in 2023 and be completed late in 2024.

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