7.2kV Circuit Breaker Close Blocking Switch 3

[nightfox1925]

We have 7.2kV, 1200A, ABB Advac Circuit Breaker feeders. In the associated breaker internal wiring diagram, we observed that there is a "close blocking switch" in series to the closing coil/anti-pump device.

I would appreciate if anyone who had experience on these breakers share their knowledge on how this switch operate and when it operates?

Furthermore, the closing coil (52X) have 52b in series to it, does this mean that an external maintained closing input can be wired to it?

The closing circuit has some kind of rectifier (4 diodes) on its input terminal. I'm still trying to contact the manufacturer for this..but a heads up opinion is appreciated.

Thanks and regards...

 

[nightfox1925]

In reference to above..I can't find anything on this "close blocking switch" in the manual. The manual, says that the closing coil is not rated for continuous duty (however, I was thinking that a maintained close signal may be used since a 52b contact is in series to the closing coil and same principle applies like to a trip coil and lockout relay contact).

 

[racobb]

The block close could be the 69 switch. It is often called the panic switch, emergency trip/block close. It is a manual, as opposed to electrical, release of the trip spring. The lever also operates a switch that blocks closing until reset. It could also be for a lockout switch contact, or any input you wanted to use to block closing of the breaker.

The 52b contact is to make sure that the close signal is removed from the coil once the breaker closes.

The diode bridge allows them to use a DC close coil on an AC close breaker. Have never liked it because it is another component to fail...and they do!

Electrically you could use a maintained close signal however the breaker would reclose as soon as it is tripped with the obvious consequences. Older style reclosing relays are often configured this way.

Alan

 

[switchgearman]

The close block switch is mounted on the breaker truck and part of the racking mechanism. It only closes in the disconnect, test and connected position. When the position pin drops thorough a hole in the racking screw the switch closes and the breaker will close electrically. It allows electrical operation only in the test and connect positions when in the cell, and disconnect at the test station.

 

[Jon47532]

I believe switchgearman is correct and the breaker has to be in one of the three positions to close. I attached the manual for the breaker in case you don't have it.

 

[nightfox1925]

Thank you gentlemen for your posts.

Our circuit breaker coil burned open. ABB inspected it at site and the initial comment is that the breaker may have been subjected to continuous current flow.

I was wondering how will that gonna happen if there is a 52a contact that drops-out the coil after a succesful close.

Is it possible that these contact may have failed to open? If this is a possibility, what may caused it?

 

[racobb]

First off a 52a would not open with the breaker closed...it is a 52b contact. Otherwise are you assuming that the breaker closed when it got the signal to close, maybe it did not. If the close command was long enough and it did not close, then it would burn up the close coil in a very short time. I have had to put out the fire.

As for the switches, yes they can go bad, become mis-aligned, or become loose in their mounts. Have seen all of the above.

Alan