Vacuum Circuit Breaker Trip Circuits 5

[tmaly1]

We're about to replace old oil CB with new GE-VAC CB. Control dwgs for new CB shows two outputs to each of Remote Trip Ckt. and Remote Close ckt. Any advice on how best to utilize each of these 4 ckts (to the two remote trip and two remote close ckts)?

In the old breaker we had a Low Pressure Alarm ckt., what the equivelant alarm should be for the new VAC CB?

Thanks folks for your help and feedback

best regards,

 

[dpc]

There's no alarm function in the vacuum breaker. The vacuum bottles are not monitored for vacuum integrity.

I'm not quite clear on the remote close and trip question. You can connect whatever you want to operate the breaker to these inputs.

Does the new vacuum breaker have dual trip coils by chance?

 

[RalphChristie]

Agree with dpc

Probably there will be more than one close coil and trip coil. You can use it for whatever you want, local switching, remote switching, auto reclose etc. for the closing coils and local switch-off, remote switch-off, normal tripping, back-up tripping etc. for the tripping coils.

Are you changing your total electrical installation (new braker, control circuits, tripping circuits etc), or just the breaker?

 

[busbar]

 

…two outputs to each of Remote Trip Ckt. and Remote Close ckt.

Does the OP mean “two inputs to each pair of trip and close solenoids”? [It is routine to furnish multiple {more than two} 52a/52b “output” contacts in modern MV/HV circuit breakers.]

As for trip/close solenoid coils, it could be the vendor had an extra breaker abandoned from an earlier order with special-order dual-trip/-close coils that he just happened to unload on you “at no extra charge.”

 

[shersan]

Low pressure alarm trip contacts possibly irrelevent in the VCB circuit breaker .

Other available contacts can be used in the modified trip circuit for VCB panels

 

[tmaly1]

Dear Folks, Thank you all for your help. You were right, I looked at the control/wiring dwgs, there is no alarm function or pressure status contacts associated with the VAC-CB.

The trip coil ckt. has two 'a' contacts in series with it, these we're taking to SCADA, another paraller trip ckt. has 'b' contact which is what confusing me what to do with it!!!!!!!!!

As for the closing coil ckt., one O/P we're taking to a GE-reclosing relay (we'll operate the CB on 3-reclose attempts before lock-out), the other we decided to take to SCADA.

 

[jghrist]

I'm not sure what you mean by taking the two "a" contacts that are in series with the trip coil to SCADA. These "a" contacts are to de-energize the trip coil when the breaker is open. They are used - you need to take a spare "a" contact to SCADA for indication.

Are you saying that there is a second trip coil with a "b" contact in series with it? This makes no sense because then the trip coil would only be energized if the breaker is already open.

 

[davidbeach]

Are you saying that there is a second trip coil with a "b" contact in series with it? This makes no sense because then the trip coil would only be energized if the breaker is already open.

But close coils usually have "b" contacts in series for exactly the same reason that the trip coil has "a" contacts in series.

The relay contacts that make to trip and close the breaker could very well be unable to break the coil circuit and depend on the heavier "a" and "b" contacts to do the circuit breaking.

 

[tmaly1]

jghrist, I'm sorry for the confusion, I meant taking one of the aux. contacts to SCADA, the two 'a' contacts I mentioned are internally wired and I won't change that.

Does anyone know what does the R and G means in the 89 Control Switch Circuit (Selector Switch)??

 

[jghrist]

Maybe Red and Green indicator lights?

 

[DiscoP]

For trip circuit supervision you use 2 'a' contacts and one 'b' contact.

The breakers we use have a Trip Circuit Supervision (TCS) terminal.

A simple explantion is from the TCS terminal there is one 'b' contact direct to the trip coil. There is also a parallel circuit through two 'a' contacts in series to the trip coil.

There is a terminal between the two 'a' contacts which the trip contact is connected to.

The TCS relay is connected to the DC +ve on one side and to the TCS breaker terminal on the other. The relay remains energised while everything is healthy.

I would guess that this is what it is for.

 

[tmaly1]

jghrist,

Thanks so much, you got it right, I thought they would label the circuits (T=Trip, C=Close), instead they labeled them G=Green, R=Red, as you wisely guessed.

DiscoP,

That is very much what we have on the VAC-Breaker, my guess would be the two 'a' series contacts serve as back-up to one another in case one of them gets 'sticky' and doesn't open in timely manner (one of them operating is sufficient if the other gets stuck!!). That's also what DavidBeach hinted to in his message.

In my case, we're using the other 'leg' for the trip Ckt. for 89 Manual Trip/Close in the control house.

Thank you all again for your feedback and help

 

[DiscoP]

tmaly1

The two 'a' contact don't really back each other up.

The trip circuit is a trip contact in series with an 'a' contact in series with the trip coil.

The second 'a' contact is to keep the trip circuit supervision relay picked up when the breaker is closed.

If you don't use a trip cicuit supervision relay, then only one 'a' contact is required in the trip coil circuit (and no 'b' contacts).

I hope this can be followed - it is difficult to clearly explain without a drawing !

 

[tmaly1]

DiscoP,

Thanks for clearing the function of the two 'a' contacts, it didn't seem to make any sense to me before you explained it.

in the old breakers, the two 'a' contacts were in series and we did have access to the node between them, we took the first 'a' contact to a remote trip ckt and the second 'a' contact to manual trip switch.

It seems in the new breakers, we won't have access to the first 'a' contact as they're connected together internally and the terminal connecting them is not accessible, do you think it will be a problem if we take the two ckts I described earlier off the second 'a' contact alone??

Thanks again

 

[DiscoP]

I don't fully understand how the breaker you have is connected, however both the remote trip and local trip should go to the trip coil via an 'a' contact.

In our breakers we have the control trip contacts in parallel - then to the same 'a' contact - then on to the trip coil.