Towards the superconducting fault current limiter

The advent of low-loss AC superconductor wires opens the way to a new current limiting technique: that of extremely fast transition from a superconducting state to a resistive state when the fault current exceeds the conductor´s critical current. A 25 kV single-phase prototype is described which consists of a Nb Ti superconducting coil without iron core and with very low inductance, lodged inside a conventional cryostat with liquid helium; each terminal of the coil is linked to a current lead and to a voltage bushing. The results obtained in power tests with a voltage of up to 16 kV and and a short-circuit current of up to 15 kA are given. the fault current, limited to 350 A in a few microseconds, confirms the feasibility of this type of current limiting device