2000A Main Tripped

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SpiderMT

Member
Had a service call today to check out a breaker that had tripped earlier in the week. Turns out it was the 2000A main w/ GFP. They had called the utility company and they told them to have an EC come out to look at the bussing and check for bad connections there.
I wasn't able to open all sections and look at all the bussing but what i saw all looked good. I also have an IR camera and there is no excessive heat anywhere i could see so I don't think that overcurrent from loose connections was the problem.
They did have a new piece of equipment installed the week before and the only thing I could think was that maybe there was a small ground fault in the motor and that tripped the Main because of the ground fault protection. This is the first time this has occured as far as anyone there could remember and it was 3 days ago so it is kind of hard to backtrack and they haven't had any problem since.
I'm just wondering if anyone with more experience with these large GFP'd breakers tripping has any better ideas on things to look for.
 
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SpiderMT

Member
Augie, I didn't read the whole thread but I don't think it is a coordination issue. There was a certification sticker from a local commissioning engineer on the main. I have used him in the past and he is pretty good.
 
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hillbilly1

Senior Member
Location
North Georgia mountains
Occupation
Owner/electrical contractor
Did the new piece of equipment use a neutral connection? If so somebody may have inadvertantly bonded it to the equipment ground, this creates an alternate path for neutral current and can cause the GF CT to detect current when there shouldn't be. Just something else to check if other ground faults are not found. Also another thing to check is in some gear, the ground fault CT is the large window type, if some of the service conductors were run outside the window it will fool the sensor into thinking theres a fault if large loads are cut on. I found this problem on one where some of the wires were cut too short and were routed outside the window instead of through it. When a large air compressor was added to the plant, the current "unbalance" was enough to trip the ground fault detection.
 
brian john

brian john

Senior Member
Location
Leesburg, VA
That there is a sticker means the GFP operated properly not that there was a coordination study.

1. Did you look at the controls? You say there is GFP, is there Phase Failure, Under Voltage, Over Voltage, Blown Fuse Trip? What model GFP, Is there a GFP trip indicator, did it show a trip?
2. GFP Relays are electronic devices these do go bad, RETEST. Additionally I recently have had 2 CT's that were not properly installed, CT would open due to loose hardware with the split CT.
3. Did you check the GFP settings? What are they?
4. Did you measure the current on the neutral ground bond?
5. Did any downstream circuit breakers trip?
6. Was there any demolition/construction going on in the facility?
7. Ask for the GFP test report and see if the "ENGINEER" tested the neutral to ground with the neutral disconnect link removed.
8. Who reset the main switch? Were the qualified, what if they closed this switch into a fault?
9. After a GFP trip there are several steps that IMO MUST BE TAKEN, I have posted what I feel these basic steps are, I can post a link to these if you IM me.
 
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G._S._Ohm

Senior Member
Location
DC area
Are there power line transients that can cause a perfectly designed and perfectly working setup to fail in this way?
How likely are they?

I guess I would step through whatever procedures are reasonably necessary to demonstrate that you have shown due diligence in debugging this.
You still may not find the problem, however.
 
zog

zog

Senior Member
Location
Charlotte, NC
G._S._Ohm said:
I guess I would step through whatever procedures are reasonably necessary to demonstrate that you have shown due diligence in debugging this.
You still may not find the problem, however.
Click to expand...

Or call a testing company, this is everyday stuff for them.
 
brian john

brian john

Senior Member
Location
Leesburg, VA
Where are you located?

If you have a phase failure relay, UV or OV relay, the switch can trip as fast as the time delay allows.

We had some very old mid 1970-1980, that were tripping, we installed a line disturbance analyzer and every time we had a transient above a certain voltage level the GFP would trip. This was in the 90's so I have no memory of the voltage level that resulted in the trips.

I'm curious as to what credentials such a company would have.
Click to expand...
,

Barely literate, barely got out of high school and barely walking upright.
 
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SpiderMT

Member
That there is a sticker means the GFP operated properly not that there was a coordination study.
True, when we have used him in the past coordination studies were done but that does not mean that one was in this case.

1. Did you look at the controls? You say there is GFP, is there Phase Failure, Under Voltage, Over Voltage, Blown Fuse Trip? What model GFP, Is there a GFP trip indicator, did it show a trip?
I have the model info at the office. I saw no trip indicator or anything for under/over voltage etc. I will post additional info tomorrow.

2. GFP Relays are electronic devices these do go bad, RETEST. Additionally I recently have had 2 CT's that were not properly installed, CT would open due to loose hardware with the split CT.
If this happens again this will be on my checklist.

3. Did you check the GFP settings?Yes What are they?Ground fault was set at 400A, I will post the other setting tomorrow.

4. Did you measure the current on the neutral ground bond?
No, also now on my checklist.

5. Did any downstream circuit breakers trip?According to the customer, no.

6. Was there any demolition/construction going on in the facility?Just the new glycol pump as far as i know.

7. Ask for the GFP test report and see if the "ENGINEER" tested the neutral to ground with the neutral disconnect link removed.I will be back out there next week, I'll see if they have record of it

8. Who reset the main switch?I think he's called the cellar master? Were the qualified, what if they closed this switch into a fault?No, they were not qualified and I explained the possibilty of this happening. Hopefully they'll call before resetting if it happens again.

9. After a GFP trip there are several steps that IMO MUST BE TAKEN, I have posted what I feel these basic steps are, I can post a link to these if you IM me.
Please post the link, i would like to have that list.
 
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