A new technique to detect faults in de-energized distribution feeders

To ensure a safe re-energizing of an overhead distribution feeder after it is de-energized for an extended period, a novel fault detection technique by controlling a thyristor based device is proposed in this paper. The proposed method involves injecting a thyristor-generated controllable signal into the de-energized feeder. The feeder voltage and current responses are analyzed to determine if a fault still exists. A thyristor gating control strategy and fault detection algorithm is also proposed in this work to detect all possible types of faults that can happen in a system. Furthermore, to distinguish a stalled motor or a capacitor bank from a fault, an algorithm based on analysis of the harmonic impedance of the de-energized system is also developed. The effectiveness of the proposed method has been verified through theoretical analysis, computer simulations and lab tests.