GFP on 2000A Main

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stevebea

stevebea

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Southeastern PA
I had a situation about a week ago on a service call to a warehouse with 480v mh high bays. A high resistance ground fault in one of the high bays was tripping the gfp on the 2000A main instead of the branch circuit OCD. I'm just wondering what could be done as far as selective coordination to eliminate this problem in the future. The shift manager was not too happy about 75 production workers standing around in the parking lot until I isolated the problem row of lights and got everything else back up online.
 
stevebea said:
I had a situation about a week ago on a service call to a warehouse with 480v mh high bays. A high resistance ground fault in one of the high bays was tripping the gfp on the 2000A main instead of the branch circuit OCD. I'm just wondering what could be done as far as selective coordination to eliminate this problem in the future. The shift manager was not too happy about 75 production workers standing around in the parking lot until I isolated the problem row of lights and got everything else back up online.
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sounds like the GFP was never set, which I seen a few times, the GFP has a setting for pickup that needs to be calculated and set by the engineer, they will come from the factory set to the lowest value, and if your not tripping the local breaker then this needs to be done, I have a movie theater that had this problem and we had to have a engineer to do a panel coordination to know the correct setting.
 
I have yet to see one that has been set until they start having problems. The factory default settings are always at minimum. As previously posted, an engineer needs to provide the settings after his/her study.
 
As noted the GFP current and delay were never set, in 30 plus years I have NEVER seen setting supplied for buildings other that data centers and hospitals otherwise coordination studies are seldom to never done.

But if your customer is willing to avoid this in the future and you work with an engineer this could be a good opportunity for you.
 
95% of engineers will tell you to contact the manufacture.

100% of the manufactures will tell you NIC, but can arrange a coordination study for a fee.
 
stevebea said:
Yes, you are correct..... factory gfp setting at 200A. Thanks guy's!
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OK, how do you know that is not correct? Tell the annoyed shift manager his company should have had a coordination study done when the place was built but they either skipped that step to save a few bucks or someone tweaked the settings because they thought they knew where ti should be set.

Do the branch breakers have GF trips? Likely they are set wrong, not the main.
 
stevebea said:
Yes, you are correct..... factory gfp setting at 200A. Thanks guy's!
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In addition to GFP we are seeing more switchboards with Phase Failure, which I feel is a mistake. I believe phase failure should be installed for sensitive equipment at the load. With restrictions on resetting mains and the immense draw backs to dumping a building during peak usage times, I feel the alternatives far outweigh the benefits of phase failures at the mains.

But then I am not an engineer and installing this protection most likely puts additional profits in some people's pockets, including me.
 
brian john said:
In addition to GFP we are seeing more switchboards with Phase Failure, which I feel is a mistake. I believe phase failure should be installed for sensitive equipment at the load. With restrictions on resetting mains and the immense draw backs to dumping a building during peak usage times, I feel the alternatives far outweigh the benefits of phase failures at the mains.

But then I am not an engineer and installing this protection most likely puts additional profits in some people's pockets, including me.
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I agree, I went on a call a few years back where the phase loss relay failed, shut down the entire high rise. The gear was very old too, looked to have been built in the 60's.
 
Every main we install arrives set as fast and sensitive as the ranges allow and will not be adjusted differently unless we get the info from the jobs engineer. Many times this never happens or at least not until they have some trips.
 
iwire said:
What?

We have to be talking about different things.
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If only the main has GF then there is nothing to coordinate it with now is there? It should be set to the minimum setting, which is the same thing you just said, so I have no idea why you think we are talking about different things.
 
zog said:
If only the main has GF then there is nothing to coordinate it with now is there? It should be set to the minimum setting, which is the same thing you just said, so I have no idea why you think we are talking about different things.
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Because there is no way the breakers I am talking about can be left set at the minimums and be expected not to trip for simple branch circuit faults.

Here is one I was sent to on 6/23/10 because it triped, it is the 1600 amp service main of a supermarket and a 20 amp 277 volt lighting branch circuit short had caused this to trip. That is unacceptable and is not coordinated with the other breakers in the building.


This is how it was set on my arrival.
62310025.jpg


One of two things is going to happen, this breaker may be removed entirely and swapped for MLO or an engineer will provide us with the correct settings.
 
iwire said:
Because there is no way the breakers I am talking about can be left set at the minimums and be expected not to trip for simple branch circuit faults.

Here is one I was sent to on 6/23/10 because it triped, it is the 1600 amp service main of a supermarket and a 20 amp 277 volt lighting branch circuit short had caused this to trip. That is unacceptable and is not coordinated with the other breakers in the building.


This is how it was set on my arrival.
62310025.jpg


One of two things is going to happen, this breaker may be removed entirely and swapped for MLO or an engineer will provide us with the correct settings.
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THis breaker will trip for 2 reasons, 3200A present for a short duration of time (Not the 0.1 seconds you may think it is, a little longer than that), or 200A GF current. Now if you have single phase loads that are unbalanced it may cause a false trip here, depending on the way your system and CT's are set up. But, a 20A circuit tripping this breaker is either a problem with the breaker protection that circuit or a GF and no other breakers in our system have GF protection. Basic selective coordination stuff, but people always want to blame the settings on the main and "crank it up" instead of finding the true problem.

I see this all the time, (and testing guy like Brian John can attest), when you have an issue with coordination, the very first step is to go look for the breaker that someone "cranked all the way up", and you find it nearly every time.
 
zog said:
I see this all the time, (and testing guy like Brian John can attest), when you have an issue with coordination, the very first step is to go look for the breaker that someone "cranked all the way up", and you find it nearly every time.
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The branch breakers are not adjustable, they cannot be cranked up.

A 20 amp 277 volt circuit faulting to ground can produce 200 amp of GF current.
 
zog said:
If only the main has GF then there is nothing to coordinate it with now is there? It should be set to the minimum setting....
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Please give me a break, you've got to be kidding, leave the engineering to engineers, and what ever 'aghast' comments I can think of.

The GFP absolutely may be able to be coordinated with the branch circuit breakers. In fact, I don't think I have never been able to coordinate with 30A, and some times higher, branch devices.
 
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