Design and Test of an Air Coil Superconducting Fault Current Limiter Demonstrator

This paper discusses the design, set-up and short-circuit testing of an air coil superconducting fault current limiter demonstrator. The demonstrator was specified for 60 kVA, 400 V, z = 6%. It consists of a primary winding made of copper, which is basically the equivalent of an air core reactor and a secondary superconducting winding made of commercially available (RE)BCO tapes, which are individually short-circuited. Both windings are inductively coupled and intended to work in liquid nitrogen. The measurements results show significantly lower impedance during normal operation compared to the air core reactor. If a fault current occurs the induced current in the secondary winding quenches the superconducting tapes, which generates a resistance and significantly increasing the impedance of the limiter. The built demonstrator achieves a current limiting capability of up to 40% for fault currents 17 times higher than the nominal current. The demonstrator proves the concept of the air coil superconducting fault current limiter and verifies the underlying design method.