Anti-Pump Relay

The anti-pump relay provides an important function feature in control circuits. Without the anti-pump function, if the user connected a maintained contact in the close circuit, and the circuit breaker were closed into a fault current, the protective relays would cause an immediate trip action, but the maintained contact in the close circuit would initiate closing (again) into the fault. This process is called “pumping”, and would lead to ultimate catastrophic failure of some element in the system, perhaps the conductors leading to the fault, perhaps the circuit breaker, or elsewhere in the system. Therefore, anti-pump is one of the fundamental requirements for every medium-voltage circuit breaker.

Recently I came across a medium voltage circuit breaker, 13.8kV to be exact, that had an issue with an Anti-pump relay. Any time I perform maintenance on a breaker, I try to do as many tests to it that I can. One of those tests is the Anti-Pump relay test, or the “Y” Relay test.

This is such an easy, yet very important test that can be performed in a matter of minutes. Typically there is some type of circuit breaker test station in a substation or switchgear room. A circuit breaker test station is a location that applies control voltage to a secondary disconnect. This secondary disconnect allows you to plug the control power into the breaker. This setup allows you to electrically operate your breaker out of the cell and on the floor.

Connect the breaker to the circuit breaker test station. Turn on the control power. The breaker closing mechanism should charge when control power is applied. Press the electrical close button on the test station and maintain the pressure to hold it continuously closed. Using your other hand, press the electrical trip button (while you continue to hold the close button). The breaker should trip and not do anything else. Releasing the electrical close button while your head is near the breaker, you should hear a soft “click”. This would be the anti-pump relay dropping out, no longer blocking a close and allowing normal operations again.

The problem with the anti-pump relay that was installed, was it was the wrong voltage rating. It was rated for 120/240VAC. Most medium voltage control circuits are DC voltage. If there was a loss of power, you would lose the AC voltage and need some type of backup power. A relay with a 125VDC power was installed, thus repairing the anti-pump feature.

This issue was found on a breaker that was in service. It is very important to be as thorough as possible when acceptance testing. Or this can prove that acceptance testing is very important. Thankfully, nothing happened from the time this breaker went into service and now.

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