Basic design of 22.9 kV/630 A resistive superconducting fault current limiting coil using YBCO coated conductor

Based on active developing of YBCO coated conductor (CC), various applications of the conductor have been developed recently. HTS systems offer tremendous advantages. Of them, since YBCO material has a high index number and specifications such as thickness and material of the stabilizer of the conductor can be controlled, CC has many advantages for applying to superconducting fault current limiter (SFCL). In general, coated conductor has a thick metal layer as a stabilizer above superconducting layer such as YBCO. Since SFCL plays a role of limiting fault current using high resistivity when a fault occurs, it is important for the design of SFCL to choose and design the stabilizer. In this paper, the design parameters for SFCL have been found. For optimal design, specifications of CC and reached temperature during the fault as well as winding structure are investigated by experiments. From this investigation, safe electric field intensity was 40-56 V/m under the condition of temperature limit of 300-400 K. Considering the electric field intensity and the number of stacks, total required length of coated conductor was estimated. Consequently, required length of YBCO CC already commercialized with stainless steel stabilizer is between 5.66 and 7.92 km for three-phase distribution class SFCL rated on 22.9 kV/630 A. In addition, a possible design using expected wire was also conducted.