Load Recovery Performances of Variable Impedance Superconducting Fault Current Limiting Transformers

The Superconducting Fault Current Limiting Transformers (SFCLTs) offer significant advantages such as large capacity and high efficiency. However, a challenge arises in maintaining power transmission during some short-circuit fault conditions, as this may lead to the inability of superconducting tapes to recover from quenching, resulting in damage due to overheating. A variable impedance superconducting fault current limiting transformer (VI-SFCLT) was designed as two parallel superconducting branches in a secondary winding to recover seamlessly with the system load after fault current limitation. In this manuscript, an experimental platform is constructed to test the current limiting and recovery performance of the VI-SFCLT under load current after a fault. The experimental results demonstrate that the proposed VI-SFCLT can limit the fault current to 40% lower than the normal SFCLT. The joule heat of the VI-SFCLT can be 78.3% of the normal SFCLT with the increase of fault duration, and the recovery time is at least 26.2% shorter. By incorporating a fast switch, VI-SFCLT achieves rapid recovery with load current, thereby enhancing the stability of the power grid.