Nexans and SNCF Réseau Put a Superconducting Fault Current Limiter on the Rail Network
Nexans and the French rail infrastructure manager SNCF Réseau have announced what they call a world-first use of a superconducting fault current limiter on a rail network. The device sits in the power supply and throttles short-circuit surges, then resets itself within minutes with no human intervention. It is scheduled to go into service on the Belfort-Delle line in late 2025.
A superconducting device with no conventional equivalent
On 27 June 2024, Nexans and SNCF Réseau announced the deployment of a superconducting fault current limiter (SFCL), described as a world first on the rail market. An SFCL exploits the sharp transition at the heart of superconductivity: in normal operation it carries current with almost no resistance, but a fault surge pushes the material past its limit, so it becomes resistant within milliseconds and limits the very current that triggered it.
Nexans describes the unit as acting like a shock absorber, limiting current peaks during a fault. Crucially it works in standalone mode and regenerates in less than five minutes without human intervention, cooling back to its superconducting state and rearming itself. Our applications article covers how this self-resetting behaviour works and why grids value it.
The deployment target is the Belfort-Delle line
The limiter is going onto the Belfort-Delle line, at the Bussurel substation, on a route that includes the cross-border link to Switzerland. Nexans put deployment at late 2025.
Rail power supplies are a demanding setting for the technology. Fault currents on an electrified network can be large and abrupt, and a device that limits them and then resets on its own reduces both equipment stress and downtime. The project extends superconducting applications beyond the grid cables and fusion magnets that dominate the field, into rail infrastructure. Other superconducting installations are listed in our project tracker.