4. Brittany: proposal for a new DC network

4.1 Brittany's power supply problems

Brittany's geographical position poses problems for electricity transmission and distribution.

Transmission is provided by a 400 kV AC extra-high-voltage line and a 225 kV line covering a distance of 1,523 km. It is completed by 90 kV and 63 kV high-voltage lines over a distance of 2,876 km.

On an average winter's day, the difference between the power demanded and the power supplied quickly reaches 500 MW in an hour. Under current electrification conditions in Brittany, there is no possible reserve to inject power into the Breton grid in a short space of time. Most of this power has to come from the rest of France, and in the case of Finistère, for example, which is "at the end of the line", transmission...