Interconnexion France Espagne
Interconnexion France Espagne

France’s ten-year network development plan (SDDR)

Energetic transition
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The publication of the SDDR is one of RTE’s legal responsibilities, similarly to other documents issued by the company on the subject of trends and perspectives. The public authorities must be able to rely on these documents and make them a vector for rolling out the multi-annual energy plan (abbreviated to PPE in French).


Rethinking the SDDR for the period of 2021-2035

As part of an effort initiated in 2017 to revise its scenarios, RTE submitted a new and completely revisited ten-year network development plan in 2019. Intended to serve as the matching piece of the projected supply estimate, it sets out a roadmap for making significant headway.

To begin with, the new SDDR is the outcome of a broad public consultation that was held in 2018. Additionally, and in line with the multi-annual energy plan’s general framework, as well as with the scenarios set out in the 2017 projected supply estimate, it covers a 15-year time scale (2021-2035) instead of 10 years as was previously the case.

It also sets out the methodological principles of the projected supply estimate: it adopts a multiple-scenario approach with detailed assumptions, lays out detailed financial trajectories and includes a large number of variants (consumption, geographical distribution of new renewable energy sources, of changes in the nuclear fleet, etc.). On the basis of all this data, the document describes how the industrial, social, environmental and financial challenges affecting the transmission system are changing.

A strategic environmental assessment

In line with its environmental and societal commitments, RTE has sought to conduct a strategic environmental assessment of the ten-year plan. This assessment seeks to evaluate potential effects on the environment brought about by changes to the transmission system by 2035.

The same approach was first used to establish the SDDR, which took account of environmental challenges from the very outset. With the additional publication of a strategic environmental assessment, all stakeholders and the general public are now able to properly understand and internalise these challenges.

The assessment report (see link to the intermediate version of the full report and the non-technical summary) was drawn up by an independent firm called “I Care” and submitted to the environmental authority of the CGEDD (General Council for the Environment and Sustainable Development) for approval before being submitted for public consultation.

What does the SDDR contain?

SDDR 2019 is divided into three parts: five industrial chapters, two “assessment summary” chapters and five cross-cutting chapters.


5 industrial chapters 2 "assessment summary" chapters 5 cross-cutting chapters
Replacement Regional overviews Flexible solutions
Upgrades Comprehensive trajectories Location of renewables
Digital framework   Self-consumption
Interconnections   Uncertainties
Offshore grid   Environment


The industrial chapters focus on the five PPE recommendations regarding the need to engineer the first major grid transformation since the 1980s:

  1. Start on the first grid replacements since its construction and be in a position – by 2030 – to significantly step up efforts (approx. +30%).
  2. Adapt the grid to the new energy mix: Be ready to accommodate new flows by increasing the capacity of existing lines, by building new ones, or by dismantling lines that would be less useful.
  3. Continue applying and adjusting the grid’s digital framework while raising cyber-security standards and using new technologies to reduce the need for new lines.
  4. Within the space of 15 years, double France’s interconnection capacity in order to optimise the differences in consumption and output in Europe, and achieve a balanced and economically sustainable mix by 2035.
  5. Build a network to accommodate marine energy sources.

These chapters are followed by two “assessment summary” chapters containing medium-term plans, regional perspectives and financial trajectories, followed by five cross-cutting chapters. The latter provide specific insights and sensitivity analyses (on flexibilities, uncertainties, challenges associated with the geographic location of renewables, the development of self-consumption, environmental issues, etc.).

A summary of the key issues

At the end of the full report, divided into the aforementioned chapters, the SDDR summary document sets out the main issues in relation to three focus areas. These align with the three types of challenge raised by major grid changes:

  • Societal and environmental: This part describes actions being implemented and options being considered, based on a holistic environmental approach (including reduced use of resources and regeneration of natural habitats) and a societal approach (more frequent use of buried structures).
  • Industrial: This part focuses on the identification and preparation of the main grid-upgrade projects for the next fifteen years.
  • Economic: This part summarises the expenditure required for upgrading the grid to cope with the challenges of the energy transition, whilst also identifying economic enablers in order to finance investments and control the costs incurred by the power system.
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