TOWARDS THE SUPERCONDUCTING FAULT CURRENT LIMITER

The advent of low loss alternating current superconducting wires opens the way to a whole 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. The 25 kV single phase prototype is constituted of a Nb Ti superconducting coil without iron core and 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 voltage up to 16 kV and short circuit current 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.