Anti pumping function in circuit breakers operating mechanism

The anti - pumping function stands as a crucial characteristic of control circuits. In the absence of this anti - pumping function, assume that a user connects a maintained contact within the closing circuit. When the circuit breaker is closed onto a fault current, the protective relays will promptly trigger a tripping action. However, the maintained contact in the closing circuit will attempt to close the breaker (once again) onto the fault. This repetitive and dangerous process is referred to as “pumping,” and it will ultimately result in a catastrophic failure of certain components within the system. The failure could occur in the conductors leading to the fault, the circuit breaker itself, or other parts of the system.

The anti - pumping relay is configured in such a way that it latches in as long as the closing signal persists. Once the anti - pumping relay latches in, it opens a contact within the closing circuit.

Consequently, the circuit breaker closes. But if the closing signal remains active, the closing circuit features an open contact, which effectively prevents any further closing operations for the duration of the maintained closing signal.

In the wiring diagram, this relay can be identified as K0 in the closing coil circuit, and you can find it at the bottom of the diagram.