Resistive Superconducting Fault current limiter integrated with Hybrid DC Circuit Breakers for HVDC System Protection

High voltage direct current (HVDC) transmission system in the subsea industry is being considered as an efficient power transmission solution as the number of power conductors and the reactive power consumption are minimal. However, one of the key challenges in HVDC transmission systems lies in the lack of reliability against short circuit faults. Serious faults can generate surge currents more than one hundred times the normal operating currents. These faults can result in damage to expensive equipment if circuit breakers (CBs) are not fast enough and rated for such a high level of faults. For offshore HV transmission systems, the cost of an unplanned outage as a result of a fault on a HVDC export cable is typically 10-fold to 100-fold the cost of the same failures in onshore HV networks. In view of this, it is desirable to introduce a reliable means of limiting the fault currents so that the CBs open at lower fault currents without any damage.

Resistive-type superconducting fault current limiters (R-SFCLs) made with high-temperature superconducting (HTS) tapes are expected to be the most effective, small-sized and offer reliable protection against such faults due to high critical current density and quick superconducting to normal-state transition. In this project, the fault current limiting performance of DCCB topology, without and with R-SFCL integration, is obtained. Further, the response time of various CB topologies like MCB, Resonant CB (RCB), IGBT based HCB (similar to ABB topology) and thyristor based CIHCB (also called DCCB topology) are also investigated. The integration of R-SFCL decreases the peak current flowing through the breaker, and this enables reduction in the size of breaker. Further, the power loss of CBs for different response time of R-SFCL is analyzed to select the superconductors for R-SFCL and suitable CB topology for future subsea HVDC power transmission systems.