Anti-pumping

What is ‘anti-pumping’? 

Anti-pumping is ‘against pumping’ (i.e.) prevention of ‘pumping’. 

Pumping, as you must be aware, is ‘making repeated strokes'. 

Thus, in switchgear terminology, ‘pumping’ is, sending repeated close commands to the closing coil and anti-pumping is preventing such an action. 

The reason for anti-pumping, as understood, by many ‘stalwart’ switchgear engineers, is that the closing coil is short-time rated and, thus, when pumped with repeated close commands, the closing coil might damage beyond repair. 

But wait! 

If, that – the rating of the closing coil - is the only concern, that could be solved in much economical means, like: 

i)     Make the closing coil, a continuous rated one; this, though, might make the coil slightly costlier (but, cheaper than providing an anti-pumping relay). 

ii)   Connect a 52b (N.C.) contact, in the closing circuit, in series with the closing coil. By this provision, once the breaker closes, the 52b contact would open and thus, would prevent any repeated closing command reaching the closing coil, even when the close command is maintained. And this is widely practiced in the switchgear industry (though not for anti-pumping).

But then, is this the real anti-pumping? 

No! 

Now, imagine a scenario, wherein a 52b contact is connected in series with the closing coil in the closing circuit. 

Now, assume there is fault downstream of the breaker. 

You attempt to close the breaker, unaware of the fault. 

The breaker closes. 

(Fault) current starts flowing through the breaker. 

At the same time, the 52b contact provided in series with the closing coil in the closing circuit, would open and discontinue any maintained close command from reaching the closing coil. 

Since fault current is flowing, any protection relay provided in the breaker would detect and issue a trip command to the breaker. The breaker trips. 

As soon as the breaker trips, the 52b contact provided in series with the closing coil in the closing circuit, would close again and permit any maintained close command to reach the closing coil. 

Assuming that the closing time of the breaker is 60 milli-seconds and the opening time is 40 milli-seconds, upon a ‘close-onto-fault’ attempt, as described above, the CO (Close-Open) operation would have completed in about 100 milli-seconds. 

And it is humanely impossible to release the hand from the close push button or the T-N-C Switch, turned to Close Position, 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. Even if a breaker is capable for such a CO-C operation, its life would drastically reduce.

Thus, simply connecting a 52b contact in series with the closing coil in the closing circuit, would not solve the above issue.

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.

It is, thus, aptly described in Cl. 441-16-48 of IEC 60050 (International Electrotechnical Vocabulary Chapter 441: Switchgear, Controlgear and Fuses), too, that an anti-pumping device is “a device, which prevents reclosing after a close-open operation, as long as the device initiating closing is maintained in the position for closing”. 

Vide Cl. 7.101 of IEC 62271-100, checking the operation of the anti-pumping device, is one of the Routine Tests, to be performed on each circuit breaker, by the circuit breaker manufacturer. 

Vide Cl. 10.2.102.2.7.4 of IEC 62271-100, checking the operation of the anti-pumping device, is one of the Commissioning Tests, to be performed on each circuit breaker, by the commissioning engineer. The closing command should be maintained for 1 s to 2 s in order that the anti-pumping device can be checked for effective operation. 

Hope the above article clears all the apprehensions about anti-pumping. 

K. SIVAKUMAR