A Study on Bus Voltage Sag Considering the Impedance of SFCL and Fault Conditions in Power Distribution Systems

This paper analyzes the bus voltage sags in a power distribution system with a superconducting fault current limiter (SFCL). Among various SFCLs, the composite type with a superconducting element in parallel with a current limiting reactor (CLR) is more effective than resistor-type SFCLs because it reduces the burden on the superconducting element, ac loss, and cost. First, a composite-type SFCL is modeled using PSCAD/EMTDC. Next, a power distribution system with a reclosing protective scheme is modeled. The bus voltage sags depend on the CLR magnitude in the SFCL and the fault period in the power distribution system; the magnitude of voltage sags depends on the magnitude of the fault current, and the durations of the voltage sags depend on the fault period, which is determined by the reclosing time. Therefore, the effects on voltage sags are assessed when an SFCL with various CLR magnitudes is installed in a power distribution system, and the fault duration is changed according to the reclosing time of the protective device.