Design and evaluation of a novel non-inductive unit for a high temperature superconducting fault current limiter (SFCL) with bias magnetic field

The level of the fault current is enlarged against the capacity of conventional circuit breaks in some urban power grids with the rapid increase of power load. Thus, a high-temperature superconducting fault current limiter (HT SFCL) has been suggested to provide effective and reliable protection of power devices against fault currents. This paper deals with the design of a prototype hybrid SFCL, which is integrated by a double-split reactor with asymmetric noninductively wound copper windings and a noninductive HTS magnet in series to one branch of the reactor. There is a fast switch in series to the magnet as well. The role of non-inductive magnet is for reducing the fault current in the first swing and the double-split reactor further decreases the fault current. The noninductive HTS unit is designed based on the magneto-thermal coupled model. A noninductive superconducting unit prototype is constructed using a YBCO-coated conductor and is immersed in the liquid nitrogen. A high-speed Data Acquisition System of National Instruments based on LABVIEW is built. The critical current and current impact performance for this prototype under the operating temperature of 77 K are investigated experimentally. The experimental results validate the current limiting effectiveness of the noninductive unit for the SFCL with bias magnetic field.