SACOI 3

On 28 May 2024 EDF and Terna launched a project that rebuilds almost everything about the oldest multi-terminal HVDC line in Europe except its route. SACOI has run between Sardinia, Corsica and Tuscany since 1967. Its successor, SACOI 3, keeps the three converter sites at Codrongianos, Lucciana and Suvereto, and replaces the equipment in full.

The biggest change is in the converters. Hitachi Energy, which won the contract for all three stations as part of a consortium, will supply its HVDC Light system, a voltage-source design. The old line uses thyristors. The new one is a bipole at ±200 kV and 400 MW, where the old one is a monopole rated at 300 MW.

Prysmian won the cable contract in May 2024: two HVDC subsea systems, 105 km from Suvereto to Lucciana and 16 km from Lucciana to Codrongianos, with two poles each. The project also reinforces the existing overhead line on Corsica between Lucciana and Bonifacio.

The SACOI article on Wikipedia gives the investment as about €1.35 billion, with €200 million from the REPowerEU programme, and sets out how the power is shared: 300 MW of base load between Sardinia and the mainland, and up to 100 MW for Corsica, rising to 150 MW if the separate Sardinia–Corsica link is unavailable. The Italian and French regulators approved the cross-border cost sharing in January 2024, preliminary works began in the second quarter of that year, and onshore works started in 2025.

For the BEST PATHS project, this upgrade was the point of its third demonstration, which studied VSC converters for an unbalanced bipolar link, extruded DC cables and DC-rated conductors and insulators, all with SACOI as the test case. The move to a VSC bipole matches the direction that research pointed in.

Commercial operation is forecast for 2029, some five years after the first works. The total route length of the rebuilt system, including the reinforced overhead sections, has not been published.