Speaking at a press conference on Monday, Enedis technical director Hervé Champenois said that “network failures, faults and even blackouts” are possible by Thursday. He said: “The ground accumulates a lot of heat. When temperatures reach 40C at the surface, it can get up to 80C underground.” He added that France has around 15,000 kilometres of old underground electrical cables that are especially vulnerable to high temperatures, including under major cities such as Paris and Lyon. He said that simulations run by Enedis based on
the latest weather forecasts suggested that parts of the grid could fail by Thursday, although added that backup networks are in place. READ ALSO: When will France’s ‘unprecedented’ heatwave end? Enedis is already engaged in a major project to replace thousands of kilometres of old-style cables – which are wrapped in oil-soaked paper and cannot withstand extreme heat – but many thousands of kilometres remain. They are especially used in major cities including Paris, Lyon, Marseille and Bordeaux – local authorities in Paris recently announced
an acceleration in the replacement project. The cost of adapting the network is estimated at €1.5 billion per year, and is not expected to be completed until 2050. Heat-related blackouts have already been seen in Europe, including in Sicily where towns were blacked out for several days in 2023 after temperatures soared to 48C. Scientists have warned that the world’s 80 million kilometres of power lines are largely unprepared to resist extreme temperatures. Work on the Paris cables began in 2024, with the obsolete paper-insulated
lead-covered cables (PILC), which are made of oil-impregnated paper encased in a lead sheath, gradually being replaced by a more heat-resilient version. PILC cables, which were the international standard from the late 19th century until the 1970s, were long considered highly reliable. They were wrapped in layers of oily paper intended to isolate the centre of the cable, which heats up as electrons pass through. The cables were conceived to resist temperatures up to 90C. But when heat is trapped for days under the asphalt,
they can reach 120-130C – ageing faster and eventually risking failure.
Enedis, French electricity grid, heat-related blackouts, underground cables, Hervé Champenois, Paris cables, Lyon, PILC cables