2004 Volume 124 Issue 6 Pages 843-850
The present study examines the breaking capability of a hybrid fault current-limiting circuit breaker (FCLCB) when a fault occurs at a distance l of 0, 1, 4 and 8km away from the terminals of the FCLCB. This hybrid FCLCB is composed of an air circuit breaker unit connected in series with a resistive or an inductive fault current limiter (FCL). In the model of the inductive FCL, a capacitance Cp is connected in parallel with the limiting coil to simulate a coil stray capacitance and a necessary additional capacitance. By means of Mayr equation, the time variation of the arc conductance in the air circuit breaker unit was estimated to find out the result of the current interruption (successful or failure interruption) for the hybrid FCLCB. The minimum limiting impedance required to allow the hybrid FCLCB to attain a successful interruption was found to be 5 and 7Ω for a resistive FCL unit and an inductive FCL unit with Cp=5nF, respectively. Further, in the presence of an inductive FCL unit with Cp=50 and 100nF, the limiting impedance needed to interrupt the fault current successfully for all fault locations was proved to be 3Ω or above. From the results of this study, it can be said that (1) the insertion of the FCL unit should be done on the basis of a coordination between the circuit breaker unit and the FCL unit and (2) connecting a circuit breaker in series with fault current limiters may enable us to use non-greenhouse gas as quenching medium for interrupting large currents.