Simulating Superconducting Fault Current Limiters With Open-Core and Closed-Core Using the J-A Formulation

High-value asymmetrical short-circuit currents test the robustness of electrical equipment, increasing the risk of damage to circuit breakers and substation components. Fault current limiters (FCLs) offer a viable solution to mitigate such impacts without requiring retrofits or layout changes. Among these, the superconducting fault current limiter (SFCL), particularly the saturated iron-core variant (SIC-SFCL), has shown promising performance in both DC and AC substations. This study compares two SIC-SFCL sub-topologies, open-core (OC) and closed-core (CC), through two-dimensional finite element simulations under identical conditions. The model employs the J-A formulation, which relates the current density (J) to the magnetic vector potential (A), allowing for an accurate representation of superconducting tapes. The simulations analyze the response of the SFCLs to different fault scenarios, evaluating their effectiveness in mitigating fault currents. Additionally, voltage drops during steady-state operation, magnetic flux density, and harmonic injections into the grid are examined. Results indicate that the OC configuration exhibits a 10% higher fault current limitation during the initial peak compared to the CC configuration for a 1 kA fault; this advantage increases to 12% for a 3 kA fault. The OC configuration also exhibits reduced harmonic levels compared to the CC configuration. The CC SIC-SFCL presents odd harmonics, third, fifth, seventh, and ninth, which can lead to greater magnetic losses and reduced efficiency compared to the OC model. Conversely, the steady-state voltage drop is lower in the CC configuration than in the OC one. These results highlight the trade-offs between both configurations, serving as a foundation for future SIC-SFCL projects.