Superconductor current-limiting apparatus

Superconductor current-limiting apparatus to be inserted in a line to be protected (L) and comprising two current-limiting units, each unit being constituted by a magnetic core (6A, 6B), a superconductor component (3A, 3B) and an electric coil (2A, 2B) disposed around said magnetic core, said two current-limiting units being contained in a single tank (13) filled with a dielectric cooling fluid (17), each superconductor component being disposed in an insulating cryostat (4A, 4B) filled with a cryogenic fluid, each magnetic core being part of a closed magnetic circuit, the tank having electrical bushings (14, 15, 16) and means including a circuit-breaker (D) for selectively connecting the electric coils (2A, 2B) in series with the line (L) to be protected via respective circuit-breakers (30A, 30B) in parallel;

• and wherein in normal operation one of said coils (2A) is inserted in the line (L) via circuit-breaker (30A) upon closure of circuit-breaker (D) with circuit-breaker (30B) open and electric coil (2B) out of the circuit such that in event of a fault in the line (L) current increase in the electric coil (2A) causes superconductor (3A) to change state, and wherein opening of line circuit-breaker (30A) and line circuit-breaker (D) are effected in a significantly short time of 40 milliseconds thereby permitting near instantaneous closure of circuit-breaker (30B) and circuit-breaker (D) to switch coil (2B) into the circuit while waiting for superconductor (3A) to recover its superconductivity state, thereby significantly reducing the time required for re-closing of the circuit.