HV Disconnect Position (52aa & 52bb)

[Kyle2022]

I'm having a hard time finding exactly how the 52aa and 52bb contacts work for a disconnect switch. I believe they work as follows, but please correct me if I'm wrong:

As the disconnect closes from open: 52bb opens, 52aa closes, 52b stays closed, 52a stays open
When the disconnect is closed: 52bb open, 52aa closed, 52b open, 52a closed
As the disconnect opens from closed: 52bb closes, 52aa opens, 52b stays open, 52a stays closed
When the disconnect is open: 52bb closed, 52aa open, 52b closed, 52a open

Thanks for your time,

Kyle

 

[rbulsara]

I have only heard of a and b contacts (not of aa and bb).
"a" contacts follow the state of a device (breaker or switch), that is its open when device is open and closed when the device is closed.

"b" contacts are in opposite state from that of the device. That is opens when the device is closed and closes when the device is open.

 

[Kyle2022]

Rbulsara,

Thank you sir. I am also very familiar with "a" and "b" contacts, but not so much with "aa" and "bb"

Kyle

 

[dpc]

I think you will have to rely on actual manufacturer's instruction manual - the "aa" and "bb" designations are not a standard and do not have a standard definition, AFAIK. If this is a new switch, the manufacturer's drawings should have this information. If it is an existing switch, verify by testing, if possible.

I'd be somewhat surprised if the "52a" stayed closed during travel between OPEN and CLOSED.

 

[rbulsara]

kyle:

Your understanding of behaviour of 52a and 52b contacts is not correct as you have stated.

As dpc advised check with the mfr. Do not assume anything. Why do you believe that the contacts work as you have stated?

 

[dpc]

It is fairly common to have limit switches that indicate the switch is in an intermediate position - similar to motor-operated valves. But you will have to verify the contact operation with the particular switch manufacturer.

 

[stevenal]

52 is the ANSI device number for an AC circuit breaker, not a disconnect. 89 is for a line switch. See C37.2.

 

[Kyle2022]

Thank you all for your comments. My belief that the switches behave as I have stated has no reasoning other than assumption. I was hoping that 'aa' and 'bb' contacts were standard which apparently is not the case.

The client is several states away, so I have no immediate means of testing said contacts. This is an old existing switch with very few existing drawings.

I am also aware that 52 is the device number for a circuit breaker but most of our clients use this number throughout the switchyard for any protective devices (breakers, disconnects, circuit switchers, etc.).

Thanks!

 

[BJC]

"The client is several states away"
In a state of confusion.
I think long ago I saw someone label A and B switch similar to what you have. It was their attempt to distinguish breaker mounted from stationary auxillary switches. I think thats taken care of in the ANSI standards I don't have a copy here at the moment. It can be taken care on in drawings by add the contacts.
The rest of the world gets by fine without it.
The best way to describe a switch like you have is with a table. US three coulumn "Open", "Intermediate" and "Closed". those refer to the main switch. Add a row for each contact and put an "X" in the box where the auxillary is closed.
It's a good ideal to a fouth column with a reference to the schematic it shows up on.

 

[Kyle2022]

BJC,


I did just look up 'a' vs 'aa' and 'b' vs 'bb' in the ANSI standards. It is just as you've stated.

Anyway, thanks for all your help. The problem that drove this discussion has been resolved. I was wondering why an 'aa' and 'bb' from a disconnect in series directly tripped a breaker. It turns out that this was meant as a failure mechanism.

Kyle