The Ten-Year Network Development Plan

RTE is required by law to publish a Ten-Year Network Development Plan so that public authorities can consult it and factor it into the operational application of the Multiannual Energy Programme.
In September 2019, RTE published a Ten-Year Network Development Plan, or “SDDR” in French, outlining planned changes to the transmission grid through 2035.
The CRE (Energy Regulatory Commission), in a statement dated 31 July 2020 on its review of the SDDR, said it was in agreement with the key principles of the plan. These principles focus on optimising costs associated with the adaptation of the grid to the energy transition and limiting its environmental impact.
The SDDR includes five industrial chapters based on the five recommendations in the Multiannual Energy Programme regarding the need to orchestrate the first major transformation of the grid since the 1980s:

Initiate the first renewal since the grid was built and be in a position by 2030 to considerably step up of the effort (by about 30 %).
Adapt the grid to the new mix: ability to handle increased flows by boosting capacity on existing lines, building new lines and removing those that will less necessary.
Continue to develop and adapt the digital backbone of the grid while enhancing cybersecurity controls and having new technologies operate the existing grid as close as possible to its limits, while reducing the need for new infrastructure.
Over 15 years, double France’s interconnection capacity, to take full advantage of differences between consumption and generation in Europe and end up with a mix that is balanced and economically sustainable by 2035.
Build a grid to connect marine energy capacity.

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Power lines and substations

RTE owns the largest network in Europe, comprising 106,047 km of lines. As the operator of the French power system, its mission is to guarantee customers, today and tomorrow, access to electricity supply that is affordable, safe, and clean. This notably requires investing steadily to build a transmission network that can support the economy and energies of the future.

As in previous years, the length of the RTE network evolved in 2020 with:

  • The creation of new overhead and underground lines;
  • The renewal of lines (conductors replaced);
  • The undergrounding of overhead lines;
  • The scrapping of lines.


Newly added52186238

Length of lines in service (km) Overhead Underground Total
At 31 December 2019 99 527 6 415 105 942
New 331 272 603
Renewed 279 14 293
Overhead lines buried 72 72
Scrapped -392 -8 -400
Other (placed in reserve, length adjusted, etc.) -84 -14 -98
At 31 December 2020 99 382 6 665 106 047
Change 2019 to 2020 -145 250 105

The length of underground lines in service on the transmission network increased again, with 6,665 km added, while the length of overhead lines in operation declined further to 99,382 km, per the public service contract entered into with the State in May of 2017.

In 2020, the public transmission network added more than 310 km of new lines (including newly undergrounded lines), of which 83 % underground.

RTE also renewed more than 293 km of overhead and underground lines on its network.

A number of projects were completed in 2020, including:

  • Rive-De-Gier: 15 km of power lines and 37 pylons removed from the landscape;
  • Haute-Durance programme: new power line between Serre-Ponçon and l’Argentière;
  • Completion of work to upgrade the RTE power grid in Greater Lyon;
  • Undergrounding of lines in the centre of the Oise department;
  • Completion of the MESIL project in Montpellier: 13 km of lines taken down, 36 pylons removed.

Along with power lines, substations play an important role in keeping the grid operating smoothly since they receive electrical energy and then transform and distribute it. They too require continued investment.

In 2020, 24 new substations were connected to the transmission system, 11 of which at 400 kV and 225 kV and the other 13 at 90 kV and 63 kV.
Main purposes of newly created substations

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Overhead and underground lines: Complementary technologies

As part of its public service contract with the French state, signed in May 2017, RTE committed to not increase, and even to decrease, the total length of overhead lines on its network (see chart, total overhead lines).
In 2020, 99.5 % of the new 90 kV and 63 kV lines brought into service were underground. RTE is also working to “take down” existing overhead lines. As technologies evolve, RTE is burying high-voltage lines more and more often.
Underground lines currently represent:

  • 9 % of all 63/90 kV lines;
  • 5.8 % of all 225 kV lines;
  • a negligible share of 400 kV lines (0.03 %).

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Key projects completed by RTE in 2020

Click on image to enlarge ⤴

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Projects under way and planned


↪ Click here to access the projects table ↩

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RTE investments in 2020

RTE’s investments within the scope of businesses regulated by the CRE (Energy Regulatory Commission) totalled €1,529 million in 2020.
Investments were concentrated mainly on the launch of the first three offshore wind farm connection projects – Saint Nazaire, Fécamp and Saint-Brieuc – and continued work on IFA 2, the new interconnector with England.
Work also continued during the year on the Avelin – Gavrelle project, the HVDC interconnector between France and Italy (“Savoy–Piedmont”), the connection of the CCGT plant in Landivisiau, and the restructuring of the 225 kV network in Haute-Durance.
Another highlight of 2020 was the delivery and acceptance of the buildings comprising the Transfo real estate project and the final fitting out thereof.


*Based on CRE (Energy Regulatory Commission) categories

*Based on categories used in the Ten-Year Network Development Plan (SDDR), 2019 edition
The 2021 investment plan RTE submitted to the regulator for the first year of TURPE 6 totals €1,726 million.
This programme involves the ramping up of offshore wind farm connections and the completion of primary work on the Avelin-Gavrelle project as well as the Savoy-Piedmont and IFA 2 interconnectors. Funds will also be invested to continue work on the Sud Aveyron and Haute-Durance projects, the replacement of conductors on the 400 kV Eguzon-Marmagne line, the restructuring of the 63 kV Puiseux Sandricourt line, and the undergrounding of lines by local initiative (MESIL) ahead of the 2024 Olympics.

Investments associated with transmission system infrastructure will increase to facilitate the energy transition and to renew ageing infrastructure.

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