Comparison of YBCO Tapes for the 10 kV Superconducting Bus Voltage-maintaining Device

Abstract

Short-circuit fault will cause the bus voltage to drop suddenly in AC power supply and distribution systems. The conventional solution is to use a conventional Bus Voltage-maintaining Device (BVD). However, the large fault current requires extremely high breaking capacity of circuit breakers. The BVD cannot limit the first half-wave of fault currents, which causes some loads shutdown. This paper proposed a superconducting BVD (SBVD) by installing a superconducting fault current limiter (SFCL) on the High-Speed Circuit Breaker (HSCB) branch of BVD, which can avoid the above problems and reduce economic losses. The YBCO tapes quench fast in the first half-wave of fault currents, together with the parallel reactor to limit the fault currents. The objective of this paper is to select the appropriate YBCO tapes to satisfy the requirements of the SFCL to achieve bus protection. Experimental results show that the quenched resistance and recovery time of ST-12-L tape ( $I_{c}=500\mathrm{A})$ is higher than AMSC-8602 $(I_{c}=225\mathrm{A})$ . The quenched resistance of ST-12-L tape can reach 0.1 $\Omega$ per meter when the fault current is high. Withstand voltage of ST-12-L tape is higher than AMSC-8602. It can reduce the size of SFCL by using a single ST-12-L tape with large quenched resistance. Besides, ST-12-L tape cost is lower than 8602. Thus, ST-12-L tape is more suitable for the SBVD than AMSC-8602 tape due to these properties. The SBVD can limit the fault current to below 4 kA by installing 20 meters long YBCO tape.