# Normal Power Breaker Tripping on return to normal



## Cow (Jan 16, 2008)

It sounds like the facility you're at may benefit from a coordination study to verify all the breaker settings are correct.


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## frenchelectrican (Mar 15, 2007)

I am with cow on his comment and I would get the min/max data logger to check any current is out of wack to make sure it is in the specs.


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## gpop (May 14, 2018)

When the transfer happens you would except a spike as its transferring under load. The settings do look wrong once you take this into consideration but its going to take a breaker specialist to confirm and sign off on new settings.


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## Southeast Power (Jan 18, 2009)

My concern is that it is or should be a ground fault breaker. The draw is less than 200 amps. It just doesn't seem to like the load when it goes back.


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## CoolWill (Jan 5, 2019)

Southeast Power said:


> My concern is that it is or should be a ground fault breaker. The draw is less than 200 amps. It just doesn't seem to like the load when it goes back.


This is the breaker that has the load on it when the transfer takes place? So utility power comes back, and the generator is running, and after a few seconds it transfers and the generator shuts down? It is a ground fault breaker?

Maybe the phase difference between generator and utility during the transfer is seen as a ground fault. Is there a neutral CT? Is the neutral in the transfer switch bonded to ground?


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## QMED (Sep 14, 2016)

Southeast Power said:


> This normal power breaker has been tripping out for a very long time when the transfer switch goes back to utility power.
> All of the other breakers are set the same.
> This just happens to be the breaker feeding the 1200 amp ATS we just swapped out so, I can't associate it to anything we did.
> 
> ...


Is it a 480Y/277? It looks like it should have ground fault then if its set to 1200A, assuming its the service

Some breakers show what they tripped on such as long time, short time etc. Does this one show what it's tripping on? It looks like the trip unit has a long time pick up setting and short pickup and delay. The short time delay is set to 0 which means no delay once it hits 1.5 times of either the frame rating or trip plug rating(usually). If it's tripping on short time maybe you could try turning the delay up. 

Those settings look like default settings so yeah should probably get a coordination as was mentioned. Or the breaker is bad.


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## frenchelectrican (Mar 15, 2007)

Southeast Power said:


> My concern is that it is or should be a ground fault breaker. The draw is less than 200 amps. It just doesn't seem to like the load when it goes back.


Is this system is soilded grounded Wye system or what ? I dont know what voltage you are running on this one but I am guessing if 480 Wye system you should have Ground fault protection once you hit over 1000 amp level. 

If that is on 208 volt wye it kinda a optional for ground fault ( most dont bother with it ) 

what else is on that ATS ?


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## micromind (Aug 11, 2007)

If there are transformers in the system and the instantaneous trip is set as low as it will go (especially the time element), it might see the core charge current as a fault and trip. 

The reason it does it only on utility is because the utility is 'stiffer' and can come up with more instantaneous current than the gen.


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## frenchelectrican (Mar 15, 2007)

micromind said:


> If there are transformers in the system and the instantaneous trip is set as low as it will go (especially the time element), it might see the core charge current as a fault and trip.
> 
> The reason it does it only on utility is because the utility is 'stiffer' and can come up with more instantaneous current than the gen.


That what I was thinking and I do not know how many transfomers did that location have and what size it is .,, but inrush current that will do it. just enough to get the ground fault system get little wonky on it. especially if switched back to uility source that will do that.


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## Southeast Power (Jan 18, 2009)

frenchelectrican said:


> Is this system is soilded grounded Wye system or what ? I dont know what voltage you are running on this one but I am guessing if 480 Wye system you should have Ground fault protection once you hit over 1000 amp level.
> 
> If that is on 208 volt wye it kinda a optional for ground fault ( most dont bother with it )
> 
> what else is on that ATS ?


Elevators, pump package, lighting, garage exhaust fans, all of the important loads in a 40 story building.


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## frenchelectrican (Mar 15, 2007)

Southeast Power said:


> Elevators, pump package, lighting, garage exhaust fans, all of the important loads in a 40 story building.


Jezz that is pretty good set up ., 

I would check the system carefully especially with motor loads. 

Did that place have multi numbers of transformers ?


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## pudge565 (Dec 8, 2007)

Is the ATS a make before break when returning to utility? If so, maybe the gen and utility are out of sync when they are both made and this breaker is the quicker one to trip? I'm not sure if this is possible but I suppose any kind of metering device can go bad that one is errantly reading and they aren't truly in sync.


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## joebanana (Dec 21, 2010)

Where's the documentation for the unit? If you're going to start twisting knobs, it's a good idea to know which way to go. And why. I second pudge's sync prognosis. Or, an inductance issue.


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