Mechanical operation faults of the withdrawable unit
Inability to rack the unit in or out: The circuit breaker unit cannot be racked in from the test position or racked out from the service position. This is often caused by deformed guide rails, mechanical binding, failure to release interlocking devices, or obstructions from foreign objects.
Chassis mechanism binding: Lack of long-term lubrication, detached pivot pins, or gear misalignment can cause a sudden increase in the operating torque required for the unit, potentially damaging the operating handle in severe cases.
Electrical faults regarding circuit breaker opening and closing
Failure to close:Issues such as broken control circuit wiring, poor contact in the selector switch, failure to charge the closing spring, loose aviation plugs, or an open circuit in the closing coil can prevent the circuit breaker from closing properly.
Failure to open: A stuck opening plunger, a burnt-out opening coil, or a shift in the transmission mechanism's dead-center position can prevent the circuit breaker from tripping during a fault, potentially leading to "skip-level" tripping (tripping of an upstream breaker instead of the local one).
Energy storage system anomalies:Failure of the energy storage motor to start or continuous idling is often caused by a failure of the motor circuit's microswitch to toggle, a breakdown of the energy storage rectifier bridge, or a fault within the motor itself.