To reduce the more increased fault current due to the increase of the power generation with the power demand, the superconducting fault current limiter (SFCL) has received attention as one of the effective methods to resolve the fault current problem. However, the operation of the protection device, especially dependent on the amplitude of the fault current, can be affected by the application of the SFCL. For the protection coordination between the SFCL and the over-current relay (OCR), one of the typical protection devices in the power distribution system, the resetting of operational parameters in the OCRs, which can be troublesome, is required. For these resettings of the protection devices, the fault current calculation from the power distribution system considering the impedance of the SFCL is inevitable. In this paper, the method using the voltage component as the effective parameter of the OCR for the protection of the power distribution system with the SFCL was suggested. Through the analysis on the simulation results from the modeling of the OCR, the suggested method using the voltage component in the OCR could be confirmed to be more effective compared to the previous resetting method of the OCR.

The current limiting and recovery characteristics of a trigger type superconducting fault current limiter (SFCL) using double quench, which consists of a power switch, two separated current limiting resistances and two superconducting (SC1, SC2) elements, were analyzed. The suggested trigger type SFCL can perform two fault current limiting operations (single quench operation and double quench operation) according to the amplitude of the initial fault current. In case of lower amplitude of the initial fault current, the fault current limiting operation of the SFCL can be performed through the occurrence of the single quench in SC1 element connected in series with the power switch. In case of larger amplitude of the initial fault current, the second quench in SC2 element connected in parallel with one of the separated current limiting resistances after the first quench in SC1 element occurs, namely, double quench, is contributed to the larger fault current limiting operation of the SFCL.

The penetration of wind turbine generators onto the grid has grown worldwide at unprecedented rates in recent years. This raises the concern that the tripping of wind turbine generators could potentially cause system collapses. To alleviate these concerns, wind turbine generators need to maintain connection with the grid when a grid fault occurs. This has provoked many countries to adopt low-voltage ride-through (LVRT) for wind turbine generators. The LVRT is the capability of wind turbine generators to maintain connectivity during certain periods of voltage sag. The wind turbine generators should be connected to the grid to support fault recovery. Also, wind turbine generators must provide reactive power according to the grid voltage sag. Therefore, much research has been focused on enhancing LVRT capability. To enhance LVRT capability, this paper proposes the application of a superconducting fault current limiter (SFCL) in the system. The fault current was suppressed and the voltage sag was improved through the application of the SFCL. By improving the voltage sag, the wind turbine generator and the grid were able to maintain a connection. However, suppression of the fault current can cause a problem in the overcurrent relay (OCR) trip time delay. The trip time delay was solved by OCR resetting. Through a power system computer-aided design/electromagnetic transients including DC (PSCAD/EMTDC), the enhancement of LVRT capability and improvement of the trip delay was confirmed.

In this paper, the effects on the protective coordination of a superconducting fault current limiter (SFCL) with the protective devices were analyzed. The SFCL has been noticed as the best solution to limit fault current effectively, which has continuously increased due to the expansion of the power facilities for the increased power demand. However, the application of the SFCL in the power system affects the protective coordination of the existing protective devices and can deviate their operation time from the original one. Therefore, the studies on the protective coordination considering the introduction of the SFCL are necessary prier to its installation. In this paper, the method to keep the protective coordination of the protective devices with the SFCL, which have been installed and tested in the Korea Electric Power Corporation (KEPCO) power test field, was investigated through the various case studies considering the load capacities and the impedance of the SFCL. Among the setting parameters of the protective device to meet the guideline required in the power distribution system, the time dial (TD) values of the protective device required for the protective coordination according to the load capacities and the impedance of the SFCL were derived. Through the analysis on the derived results, the lower TD value could be confirmed to be needed in the case of both the higher load capacity and the SFCL with its higher impedance.