Study on the Parameter Requirements for Resistive -Type Superconducting Fault Current Limiters Combined with Mechanical DC Circuit Breakers in Hybrid AC/DC Transmission Grids

The coordination of resistive-type superconducting fault current limiters (R-SFCLs) and DC circuit breakers (DCCBs) have been investigated. However, the use of R-SFCLs with mechanical DCCBs (M-DCCBs) in hybrid transmission systems has not been studied. The objective of this paper is to investigate the parameter requirements of R-SFCLs and M-DCCBs for a detailed system protection strategy in a hybrid AC/DC system considering the influence of AC faults and three types of DC faults. When the AC fault is far from all MMCs, its impact on the DC system is weak. If the AC fault is close to one MMC, it will produce a strong transient response in the DC part. Therefore, a bypass switch in parallel with an R-SFCL is used to remove the R-SFCL from the system if it quenches during the AC fault. Then, the parameters of the protection devices are designed based on pole-to-pole DC fault. System restoration can be achieved within 200 ms after the fault. For pole-to-neutral and pole-to-ground faults, except for the R-SFCLs at the faulty pole, the R-SFCLs at the healthy pole will also quench, but the resistances are very low. The system may be restored within 250 ms after the DC fault.