Energy storage chain for a vehicle, including at least one ultracapacitor module, energy storage system including such a chain and railway vehicle including such a system

The chain (14) has an electrical storage system (26) mechanically fastened in a metal carcass (24), and comprising supercapacitor modules (32A-34A). Each module comprises a metal enclosure (36) and a set of supercapacitors linked together in series and arranged in the metal enclosure. An electrical protection device (28) comprises a fuse, and is designed to open an electrical circuit. The electrical protection device links an element out of the metal carcass or the supercapacitor modules, to an electrical ground.