Anti Pump Relay

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Antipumping relay is used to prevent continuous closing and tripping of a circuit-breaker if the T-N-C (Trip- Neutral-Close)switch is held in close position under a fault condition. In the closing circuit of the circuit breaker NC(normally closed) contact of antipumping relay is used. The antipumping relay will get energised when the breaker is closed and will prevent subsequent closing even if T-N-C switch is held in close position. The antipumping relay will drop when the switch is brought in Neutral or Trip position.

An anti-pumping relay is used to prevent "pumping" repeated close signals inadvertently to the closing coil of a circuit breaker. Imagine a scenario, wherein there is an existing fault and the operator - unaware of the fault - attempts to close the breaker, by pressing the close push button or by turning the T-N-C Switch to the 'C' position. The breaker will attempt to close but the protective release would sense the fault and would trip the breaker. All this would happen within 100 milli seconds (assuming a closing time of 60 milli seconds and an opening time of 40 milli seconds). And, it is humanely impossible to release the hand from the close push button or the T-N-C Switch, within this 100 milli seconds. Thus, the closing signal would persist and the breaker would attempt another closure - under fault conditions. Most of the circuit breakers would not withstand such closing-under-fault conditions, twice in succession. The anti-pumping relay would prevent a second closing signal to the breaker closing coil, even if the Push Button/T-N-C Switch is kept pressed, thus avoiding the above danger.

Thank you for further elaboration and technical clarification.