On a small road, about ten kilometers from Auray (Morbihan), Enedis agents, helped by employees of service companies, carefully dismantle nearly a kilometer of electrical cables, using pulleys, to replace them with a single cable, larger and stronger.
This is one of around 3,500 projects planned by the manager of the distribution network in Brittany over the next five years. “We want to make the region the laboratory of network resilience to climate change»assures Hervé Champenois, the technical director of Enedis. Brittany has 109,000 kilometers of power lines.
A network “chopped” by the storm Ciaran
A real challenge, as storms, more frequent and more violent due to global warming, each time cause major damage to installations, many of which were built more than half a century ago. This is the case of storm Ciaran, which crossed Brittany, just a year ago, on the night of November 1 to 2, 2023, with its wind gusts of up to 207 km/h at the tip of the Raz.
The damage to the network was considerable, with trees falling on the lines, broken poles, distribution stations and transformers torn out. “An unprecedented event in Brittany, whose impact was two to three times more significant than the storms of 1999”underlines Hervé Champenois, speaking of“a chopped-up electrical network”. In total, 1.2 million homes were deprived of power in France, including 780,000 in Brittany.
Even if, in the end, more than 90% of homes were replenished in four days, the EDF subsidiary now says it wants “learn lessons” by amplifying its work program in Brittany. The investment plan adopted in the summer of 2023 planned to strengthen the reliability of 3,500 km of lines between 2025 and 2029, with a budget of 390 million euros. Enedis announced on Monday October 28 that it planned to make an additional 2,000 km more reliable, for a cost currently being finalized.
Drones to check the condition of lines
The “Reconstruction Brittany” plan thus provides for the burying of 1,100 km of lines, or 700 km more than was planned before storm Ciaran. This will mainly be done in the most accident-prone areas, where there are trees, for example. It also plans to refurbish 800 km of air network, in addition to the 2,200 km already budgeted. Drones, coupled with an artificial intelligence program, are already operating inspection flights along the cables to check which ones need to be renovated first.
Finally, a specific section concerns the gradual abandonment of wires « nus »these uninsulated copper lines, which are much more numerous in Brittany than elsewhere. In all, 1,400 km (out of 7,500 km) will be replaced by twisted wires, or 500 km more.
“The goal is for future storms to cause less damage and fewer outages, so that we can restore power to 90% of homes within forty-eight hours, twice as fast as currently»assures Pascal Pouzac, the regional director of Enedis. Switching from bare wire to twisted wire reduces the risk of incidents by seven to eight times and the planned renovation of the lines reduces the breakdown rate by 30%.
Burying the lines makes it possible to divide by ten the cases of outages in the event of a climatic event, but the price remains high: between €100 and €150 per meter compared to €20 to €25 per meter above ground. “For each project, it will be necessary to define a technical-economic optimum », Underlines Pierre-Olivier Courtois, the head of the Reconstruction Bretagne project, who also hopes to have enough subcontracting companies.
25 billion euros to adapt the network
There will be no shortage of work to develop and modernize electricity networks at a time of energy transition. Enedis mentions 96 billion euros over the period, including 25 billion euros linked to the adaptation of lines to climate change.
You have to know how to deal with storms, like in Brittany, but also floods. “For a year, we have never experienced so many»underlines Hervé Champenois. After last autumn’s floods in Hauts-de-France, Enedis decided to raise its source stations, the installations the size of half a football field which connect the RTE high voltage network and medium voltage.
There is also now an increase in heatwaves in urban areas, which can damage power lines. However, they are buried but are starting to show their age. In many large cities, cables are still surrounded by impregnated paper (CPI) normally intended to be insulating, but which seems to have poor resistance to heat, with the appearance of condensation in particular. A vast program to replace 700 km of cables per year has been launched and must be accelerated.
