Upgrading of the existing 380 kV high-voltage line between the HV substations of Gramme (municipality of Huy) in Belgium and Lonny in France.

An efficient, sustainable and reliable electricity grid

The 380 kV Lonny-Gramme line is an interconnector built in 1974, which connects the Gramme substation in Belgium to that of Lonny in France. This link is considered to be one of the backbones of the electricity grid, allowing for the cross-border exchange of electricity between Belgium and France. 

The planned upgrading of this link is essential for meeting the energy and climate challenges of the future. By optimising this infrastructure, Elia is ensuring: 

  • Enhancement of security of supply in our country, thanks to greater cross-border electricity exchange capacity with France;
  • Better integration of the European electricity market in order to encourage greater convergence of electricity prices in Europe, meaning more affordable electricity;
  • Integration of renewable energy from new generation units.

A Project of Common Interest (PCI)

The European Commission, acknowledging the project’s importance within the European context, has already qualified Lonny-Gramme as a Project of Common Interest (PCI). The Commission, in this context, is supporting cross-border infrastructure projects that interconnect the power systems of different countries and help the EU to achieve its energy policy and climate goals.

The project has been identified as necessary for the European NSI West (North-South electricity Interconnection in Western Europe) priority corridor according to the latest Union list for PCI and meets the needs of the European system from 2030 onwards on the Belgium-France border.

  • texteScope of the project

    In order to upgrade this interconnector, Elia and RTE (the French high-voltage transmission system operator) carried out a bilateral study to determine the most appropriate technologies, as well as the most optimal implementation schedule for the project.

    The studies confirm the technical feasibility of increasing the physical transmission capacity of the line by approximately 1 GW. This feasibility is conditional on the replacement of conductors and the need to carry out pylon upgrades.

    The scope of the project consists of the replacement of the existing conductors on the 380 kV AC overhead line linking Gramme (Belgium) and Lonny (France) with high-performance “High Temperature Low Sag” (HTLS) conductors and installing a second phase-shifting transformer in the Achêne substation. These works are to be completed by 2030. Given the use of high-performance conductors, modifications will be required in the 380 kV Achêne and Gramme substations. The project nevertheless involves an initial upgrade of the Achêne substation by 2025 with the installation of a first phase-shifting transformer and a 380/70 kV transformer to support local needs. 

    An HTLS (High Temperature, Low Sag) conductor is a type of cable that can carry up to twice as much current as a conventional conductor. The presence of phase-shifting transformers will permit optimal use of the capacity of the planned infrastructure. These transformers enhance flexibility by increasing the means of regulation available for Belgium, allowing for effective congestion management on these and other lines.

  • texteThe route
  • environnementEnvironment
    Elia pays particular attention to the proper execution of its projects and to the environment in which the works are carried out. Procedures are put in place for each stage, thus limiting the impact on fauna, flora, mobility and for local residents.
  • Schedule

    The Lonny-Gramme project is currently included in the 2024-2034 Federal Development Plan submitted for approval. According to the current provisional schedule, the interconnector will be upgraded around 2030 – 2032.

    • 2021-2022: exploratory studies
    • 2022-2027: technical studies, permit application procedures and tender process
    • 2027-2030: construction phase
    • 2030: commissioning 
  • texteA project that will benefit from the European Recovery Fund

    Lonny - Gramme uses the European Recovery Fund, which is intended to provide the Belgian economy with additional incentives through future-oriented initiatives. Investing in infrastructure is investing in economic growth that strengthens the socio-economic prosperity of our country.

Last update - January 2024

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