Breaker Control Diagrams

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Mike01

Mike01

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MidWest
I recently have been getting more involved with medium voltage work, but I am struggling trying to understand medium voltage circuit breaker control diagrams indicating all the relays contact(s) open/closed etc. is there anywhere I can find how to better understand / interpet these diagrams? Any help would be appreciated. Thanks.
 
Generally I will get the mfg cb manual, the protective relay manual, and the control interconnect diagram. Usually these have sections that describe the contacts, operation and timing.

With the manuals in hand, it a matter of puzzling through the schematic/interconnect diagrams. Occasionally I have had to call the mfg tech support or engineering cause something is not clear. I usually do better with engineering.

A couple of things to get started:

Medium voltage cbs generally have to have external control power to trip, although they will likely have a mechanical actuation buttons as well

52a contacts close on CB closed. 52b contacts close on CB open

SF6 breakers will have pressure switches that will either open the CB on low pressure, or inhibit opening the cb on low pressure.

There will be aux contacts that remove power from the trip and close coils as soon as the cb activates.

There will likely be two trip coils

There may be a close coil and a holding coil or just a close coil.

Ther will be a spring charging motor with attendent control contacts.

There is likely an anti-pump ckt

cf
 
MV Control

MV Control

Good luck. Every utility and company has a different approach to control. I have seen it done in a 100 different ways. Positive common, negative common. DC trip and AC close. Dual redundant relays or old electromechanical relays.

Manufacturer's circuit breaker schematics are a good starting place.
 
Cold Fusion said:
Generally I will get the mfg cb manual, the protective relay manual, and the control interconnect diagram. Usually these have sections that describe the contacts, operation and timing.

With the manuals in hand, it a matter of puzzling through the schematic/interconnect diagrams. Occasionally I have had to call the mfg tech support or engineering cause something is not clear. I usually do better with engineering.

A couple of things to get started:

Medium voltage cbs generally have to have external control power to trip, although they will likely have a mechanical actuation buttons as well

52a contacts close on CB closed. 52b contacts close on CB open

SF6 breakers will have pressure switches that will either open the CB on low pressure, or inhibit opening the cb on low pressure.

There will be aux contacts that remove power from the trip and close coils as soon as the cb activates.

There will likely be two trip coils

There may be a close coil and a holding coil or just a close coil.

Ther will be a spring charging motor with attendent control contacts.

There is likely an anti-pump ckt

cf
Click to expand...

Good post . Let me add that the mechanism could also be hydraulic , pneumatic , or in the case of the ABB R-Mag , a big damn magnetic actuator .

One of the most important things to remember when looking at the schematics , they are usually drawn with the device in the open position . No control or auxillary power applied . No air , hydraulic or SF6 pressure and springs discharged . :)
 
zog said:
and...let me add that you shouldnt assume the OEM wiring diagram is correct, many alterations are made by end users.
Click to expand...

And for some reason , the prints don't get updated and placed in the equipt . file . Nah , that only happens where I work . :mad: :mad:
 
djohns6 said:
And for some reason , the prints don't get updated and placed in the equipt . file . Nah , that only happens where I work . :mad: :mad:
Click to expand...

No kidding, I just remanufactured a breaker from 1948 to supply as a spare and the plant didnt even know what a wiring diagram was, how do they expect it to work in thier switchgear? We just had to go with the origional prints.
 
At least you had some kind of prints . We have a job pending right now to troubleshoot an automatic synchronizing circuit in a substation and there is not a print to be found ANYWHERE . Not a schematic or connection diagram . Nothing . Excuse my slightly off topic rant .
 
djohns6 said:
At least you had some kind of prints . We have a job pending right now to troubleshoot an automatic synchronizing circuit in a substation and there is not a print to be found ANYWHERE . Not a schematic or connection diagram . Nothing . Excuse my slightly off topic rant .
Click to expand...

Dont agologize, been there, done that. It is a long process.
 
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