3000 amp square D breaker problems help!

Merry Christmas
Status
Not open for further replies.
N

newsparky

Member
Location
Destin,Florida
If anyone has any information or input on this problem please let me know...

A 3000 amp square D breaker, that tested "good" keeps tripping out, we also got a small arc flash. We are unable to run on utility power due to this, we are on geneators, we have had 2 techs out and no one has any idea....:confused: This is an older breaker and converting to a new one will take a lot of time and effort that we don't have. Thanks! :D
 
newsparky said:
If anyone has any information or input on this problem please let me know...

A 3000 amp square D breaker, that tested "good" keeps tripping out, we also got a small arc flash. We are unable to run on utility power due to this, we are on geneators, we have had 2 techs out and no one has any idea....:confused: This is an older breaker and converting to a new one will take a lot of time and effort that we don't have. Thanks! :D
Click to expand...

What model breaker?
Drawout or fixed mounted?
What testing was done, primary or secondary injection?
What trip indication is being given?
What do you mean by "got a small arc flash"?
Have you had the breaker cubicle/bussing looked at?
 
First stop reclosing the CB

I'm not sure what "tests good" means. A 3000A CB has a separate trip unit and may have dozzens of settings, separate current sensors, probably even voltage sensors. Are you saying every trip unit function was checked and all of the CB electromechanical operating mechanism was checked?

The "small arcflash" also bothers me. Generally speaking 3000A and small arcflash don't go together.

The best I can tell you:

1. Believe your instrumentation. Maybe the CB trip unit is telling you the truth and is tripping for a reason. This was the lesson from "Three Mile Island".

2. You said, "keeps tripping out" and "got a small arc flash". Stop reclosing the CB until you understand why it is tripping. For one thing it is an OSHA violation. And that is the best method I can think of to turn that small arcflash into a 25KA fireball.

"This is an older breaker and converting to a new one will take a lot of time and effort that we don't have"

You have all the time in the world to do this in a manner that keeps everyone alive and uninjured.

carl
 
jim dungar said:
What model breaker?
Drawout or fixed mounted?
What testing was done, primary or secondary injection?
What trip indication is being given?
What do you mean by "got a small arc flash"?
Have you had the breaker cubicle/bussing looked at?
Click to expand...

Model number MP30H2
Drawout
No trip indication on this older model
Trip unit was tested, OK (testing done by Sq D Tech.)
Breaker showed "open" while screwing it out, got the flash, it was my first flash, (scared me) but everyone told me it could have been worse.
Did look at the cubicle/bussing all OK.
 
What model breaker? MP30H2
Drawout or fixed mounted? Drawout
What testing was done, primary or secondary injection? Test done by Sq D tech I am not sure.
What trip indication is being given? Trip unit tested OK
What do you mean by "got a small arc flash"? Breaker showed "open" so while screwing it out we got the arc flash, tested unit again tried it and it tripped.
Have you had the breaker cubicle/bussing looked at? all ok
__________________
 
I think there is still some information needed. I, at least, do not understand the sequence of events.

Start with this: “What started the events?” By that I mean was everything running nice and smooth, and suddenly the breaker tripped without warning and without any secondary indication of problems (example: just before the breaker tripped the motor was making a loud noise)? Or was the breaker taken out of service for normal maintenance, and it tripped when you tried to put it back into service?

Next, why was there a SquareD tech at your site? Did the problem with the breaker happen, and then you called the SquareD tech? Why was this person doing any testing (i.e., was it because you reported a problem to them)?

Next, did I correctly interpret you as having said that you saw the arc flash as you were racking the breaker out? Why were you racking it out? Had it indicated that it had tripped, and were you opening it up to inspect it?

I think that if the breaker showed that it was open, and if it flashed when you tried to rack it out, then it was not, in fact, open, and you, in fact, opened it while trying to rack it out. That would explain the flash; breakers do not like to open under load, especially if the load is a large motor, and especially if the method of opening the breaker is by racking it out. I would look into the breaker position indication system, to see if it is accurately reporting the breaker as being open when it is really open, and closed when it is really closed.
 
What is the voltage? 480
Is the breaker a GFP type? Yes
and as has been mentioned, it sounds like someone does not understand what they should be doing. Who is conducting this "mess" for you? no comment
__________________
 
breaker was taken out of service for normal maintenance, (6 hour generator run) and it tripped when we tried to put it back into service
Sq D called out to test the trip unit.
We were opening to inspect it.
 
My next move would still be to look into the breaker position indicator. I still think that it is possible that the breaker was still closed, regardless of what the indicator said, when you tried to rack it out.

But let me ask a follow up question, the answer to which might disprove my theory. How did you accomplish the shift from generator to normal source? Did you parallel the utility with the generator, and did the breaker trip (or at least show that it tripped, whether or not it really stayed closed) at that time? Or did you manually trip off the generator?s breaker, and then attempt to close the normal breaker?
 
What is the breaker type? Never heard of a MP3OH2, that must be a different number, the type should be DS-532 or something if it is a drawout breaker. Please post the Type.

Sounds like a CT problem, testing the trip unit via secondary injection will not find this, you need a primary injection test to verify. I can have a tech there today to evaluate.

I can get you a replacement breaker by tommorow to use while your breaker is tested and repaired. PM me if you need some details.
 
I will echo Zog's commnet on this one and something else somehow it click in my mind with this part.,,

is this have manual recloser or motor driven recloser device ?? if the latter somehow the cam and interlock is not in sychrounus.


[ i will never derack that sonvagunner underload at all it is good way to ruin a expenisve bussbar for sure. ]

Merci, Marc
 
The MP breaker is one of the early generation MasterPact it has been replaced by the MasterPact NW family. The bare bones trip units did not include trip indicators.

If the Square D techs did not perform a primary injection test then you have not checked the breaker completely (a secondary injection only tests the trip unit's electronics).
 
For some reason I thought the OP said an old square d breaker, must have been thinking about another post. Wasnt even thinking about Masterpact.
 
zog said:
For some reason I thought the OP said an old square d breaker, must have been thinking about another post. Wasnt even thinking about Masterpact.
Click to expand...

Square D has been selling the Merlin-Gerin Masterpact family in the US for at least 10 yrs (I see the MP032 in my 1997 Digest).

When I hear "old electrical" for some reason I always think back 30-40yrs, which is a lot easier than remembring why I just walked into a room.:roll:
 
how often is this type of breaker inspectin performed. seems like there was no backup plan, if it was found faulty. is this a plant thing, or was an outside EC brought in to do this?
 
breaker

breaker

My question is why would the breaker draw a flash while you are racking it out and it is in the open position. Their should have been no load going through it unless one of the phases on the line side went to ground.
 
breaker

breaker

Did you megger the breaker phase to phase while open and closed.
also megger the breaker line to load while open. and phase to ground while closed. The flash could have been one phase not completly open or even a phase to phase arc.
 
Look at sequence of events as CharlieB illustrated. This will help determine the cause, and not the resultant. "small" arc flash? I highly doubt it was a small arc flash, as defined. Not at 3000A and generators capable of feeding the fault. The contacts on one of the poles could have been slightly welded together, then parted. A visual inspection of the contacts can tell you this.

No matter what, I say you need a re-build on the breaker, and a new trip unit. SQ-D should be able to do this for you on sight. They should also be able to ship in a new or rebuilt breaker pretty quickly as well.

For the sake of safety, DO NOT RUSH TO A QUICK FIX no matter how hard management is breathing down your neck.
 
Thanks!

Thanks!

Thank you for all your information and input, this situation has been taken away from our electrical department and now is in the hands of engineers, fine with me! :wink: One arc flash is one too many for me! I called it "small" because my supervisors and I were not burn up....thanks again for all the help!
 
Status
Not open for further replies.
Top