Current Limiting Characteristics of Inductive Type SCFCL With ZnO Device and Resistor in Parallel

A new FCL system which consists of a L-type SCFCL in parallel with a resistor and a ZnO device is proposed. The proposed system limits the fault current inductively and also consumes excessive energy like R-type ones. A model system was made and studied experimentally. The ZnO device is off-state in stand-by mode. When a fault occurs, the SCFCL turns into current limiting mode and has high impedance. The voltage across the SCFCL exceeds a threshold voltage of the ZnO device. During one cycle of the voltage, the ZnO device is on-state around the peak of the voltage, and the current flows through both the SCFCL and the resistor. A certain amount of excessive energy is dissipated in the resistor. The ZnO device is off-state around the peak of the current which is suppressed only by the L-type SCFCL. Finally the proposed FCL system switches L-type and L+R-type in a cycle. Relations among the threshold voltage, the current limiting impedance and the resistance of the resistor were discussed. It was confirmed the proposed FCL system represents desirable current limiting characteristics.