Circuit Breaker Failure to Operate or Maloperation: Check the energy storage mechanism, closing/tripping coils, auxiliary switches, and secondary circuits. High-Voltage Fuse Blown: Measure voltage across the fuse terminals; inspect busbar joints, cable terminations, and. Common methods of protecting busbars include overcurrent-based interlocking schemes, overcurrent-based differential protection, high-impedance differential protection, and percentage differential protection. Busbars have typically been left without dedicated protection, from the following reasons: It is a fact that the risk of a short circuit happening on modern metal clad equipment is insignificant, but it cannot be completely dismissed. Nevertheless, the damage resulting from one short circuit may be. In the event of a major disturbance on the system that caused an under frequency event, the relays would trip the main 140 kV breaker feeding the mine. If the mine owned relay was the only one to trip, the mine could go back online in stages. A busbar protection must be capable of clearing all phase-to-earth faults, and in the case where they can occur, phase-to-phase faults. Policy regarding fault clearance times required from busbar protection varies from utility to utility.
