Help!! Power Quality Issues Multiple Office UPS's Going Off Randomly!

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I work for a college. We are currently having some ups's going off randomly through out the day. The problem is that it is only happening on the 3rd floor of this building. It has 2 transformers on the third floor 480 to 120/208 4 panels 120/208. 2 panels on each transformer. One transformer is a 75 kva and the other is 112.5 kva. Randomly the UPS's start going off. Sometimes last for 1 min or 40 min. We replaced both of these transformers about 3 years ago and it cleared up the problem. Recently the problem is back. We replaced the 112.5 kva transformer and it cleared the problem for about 3 weeks and now it is back. Traced the circuits and the problem is coming from both transformers. Wondering if i should try to replace the 75 kva transformer next? It doesn't happen to all ups's just certain ones. Wonder if it is the tolerance rating on each ups. There is a computer cluster there with identical ups's that where being affected. We changed the settings to poor power quality and theses ups's haven't had a problem. I have been monitoring the power with an Amprobe DMIII. Problem is i don't know what i am looking for. Do any of you guys have experience reading Amprobe software? Also this building is tied to the same high volt that feeds another building we were having amperage going to ground. Check out this forum. http://forums.mikeholt.com/showthread.php?t=162996&page=8
They keep asking for answers and i don't know what to tell them. Called a couple of company's to look at it and they said it would be 7,000 to hook there meters up for a week. That isn't even solving my problem just them collecting data. I can email all of the data i collected if some one can make sense of it. I can admit that the cooling went out in there and it exceeded 105 degrees. i also have the option to transfer the high volt to another circuit. We have 3 separate feeds that come on to campus. What is strange is that only the 3rd floor has this problem. All help would be appreciated.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
141022-1358 EDT

Many UPS units have an output that will provide information from the UPS. For example voltage. Start monitoring a unit that has triggered in the past and has this monitoring capability.

Before starting the monitoring on your building supply, get a Variac (trademark of General Radio) or other brand variable transformer, and change the input voltage over the range of 90 to 140 V. Use a good digital meter with accuracy and resolution of 0.1 V at 120 V to monitor the input voltage to the test UPS as you adjust the voltage. Determine high and low threshold points. There is probably no high threshold. Correlate the DVM with the UPS data output. Record and graph all your measurements. There is probably hysteresis at the UPS threshold point.

Put the test UPS on your power system and start the computer monitoring the UPS.

Next use the same digital meter as above to check your wall voltage at various places on your third floor. Then to a floor where there is no problem.

.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
141022-1427 EDT

I have a UPS that switches to backup at about 99 and returns to wall power about 105 V. Backup voltage is about 111 V with no load. At the high end goes to backup about 129 V and back to wall power aabout 125 V.

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iceworm

Curmudgeon still using printed IEEE Color Books
Location
North of the 65 parallel
Occupation
EE (Field - as little design as possible)
5 S -
A couple of questions:
It has 2 transformers on the third floor 480 to 120/208 4 panels 120/208. ...
I'm guessing you meant the transformers secondaries and panels are both 3 phase 208/120?

... We replaced both of these transformers about 3 years ago and it cleared up the problem. Recently the problem is back. We replaced the 112.5 kva transformer and it cleared the problem for about 3 weeks and now it is back. Traced the circuits and the problem is coming from both transformers. Wondering if i should try to replace the 75 kva transformer next? ....

What made you suspect the transformers? What was/is the evidence the transformers were causing the problems?

.... Called a couple of company's to look at it and they said it would be 7,000 to hook there meters up for a week. That isn't even solving my problem just them collecting data. ....
$7K doesn't sound like that much compared to buying and replacing a transformer - especially if there is no evidence there is anything wrong with it. Short of bad connections and flat burning up, transformers don't tend to cause power problems.

I'd suggest getting a quote for a report on the data collected. Just data collection alone won't help.

... Problem is i don't know what i am looking for.

... They keep asking for answers and i don't know what to tell them. ....

Try, "We are not getting any clear answers from our analysis. We need a specialist."

ice
 
"I'm guessing you meant the transformers secondaries and panels are both 3 phase 208/120?"

Yes

"What made you suspect the transformers? What was/is the evidence the transformers were causing the problems?"

The transformers were subjected to high temps. They are rated for 40C max. We eceeded that in that room for a period of time. No evidence just a guess.

"$7K doesn't sound like that much compared to buying and replacing a transformer - especially if there is no evidence there is anything wrong with it. Short of bad connections and flat burning up, transformers don't tend to cause power problems."

Both transformers were about $2,300. We replaced them in house so no charge on labor.

"I'd suggest getting a quote for a report on the data collected. Just data collection alone won't help."

Do you know anybody that deals with Amprobe data? Most companies I called deal with Fluke.

Sorry trying to figure out how to attach quotes like you did.

Thanks for the HELP!
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
...
The transformers were subjected to high temps. They are rated for 40C max. We eceeded that in that room for a period of time. No evidence just a guess.
...
The transformers are rated for a rise over the ambient. The 40?C would be the maximum permitted ambient. The rise would often be 80?C or even 115?C over the maximum ambient. There is not an issue unless the winding temperature exceeds the permitted rise plus the maximum ambient. Even where the temperature has exceeded that value, you mostly just shorten the life of the transformer. It would be very unlikely that it would cause any type of power quality issue.
 

GoldDigger

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You can quote the whole post using the Reply With Quote button on the full website or if using Tapatalk you select the post you want to quote and then use the Quote icon which appears at the top.
 
I belive my problem Is harmonics. Just read some info on a site about harmonics.
http://m.ecmweb.com/archive/harmonics-made-simple
I will post some of the data I recorded tomorrow.
I kind of wish I read this sooner looks like I might need k rated transformers. Does anybody know anything about harmonics? Do usp's cause harmonics? I might have to go through every room and see what equipment is running? When I go through my data at the time of glitches, the only thing out of the norm is the harmonics raise a little. Like I said I'm no professional in this type of problem. Give the problem that the guy has with the dryer not working and lights dimming I'll figure that one out.

Again I appreciate all the input!
 
Don't go chasing harmonics. I can't say it's not your problem but 90% of the time it's not.

Why is it random? Why is it only the 3rd floor? This floor has its own 480 v panel not tied to any motor loads. It feeds the 2 transformers and lighting. Do you think a breaker off the mdp could cause all of this randoness problems? It is not a problem that occurs all day. Some days nothing happens and other days it happen 1, 2, 3, times never can tell.
 
I have also used a thermal cam on this. There is no hot spots. The only "hot" spot is the 3rd leg bus bar on the 480 panel. And it is only 86 degrees f. All bolts and ever thing is tight. I am very stumped on this problem. The only thing I can think of is harmonics. I watched the meter one day and the harmonics came out of sync while a surge was happening. I do show voltage anomalys. They are surging and lasting a couple of hours. Go to the voltage readings and everything is in the norm? It shows high lows and average every 5 sec. Mabey my meter needs to be calibrated?
 
Why is it random? Why is it only the 3rd floor? This floor has its own 480 v panel not tied to any motor loads. It feeds the 2 transformers and lighting. Do you think a breaker off the mdp could cause all of this randoness problems? It is not a problem that occurs all day. Some days nothing happens and other days it happen 1, 2, 3, times never can tell.

I have also used a thermal cam on this. There is no hot spots. The only "hot" spot is the 3rd leg bus bar on the 480 panel. And it is only 86 degrees f. All bolts and ever thing is tight. I am very stumped on this problem. The only thing I can think of is harmonics. I watched the meter one day and the harmonics came out of sync while a surge was happening. I do show voltage anomalys. They are surging and lasting a couple of hours. Go to the voltage readings and everything is in the norm? It shows high lows and average every 5 sec. Mabey my meter needs to be calibrated?

Sorry meant to say the wave came out of sync... it had a bunch of ripples.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min from the winged horses.
Occupation
Licensed Electrician
I wish it was nonsense the problem is present.
Take a breath. You have three floors, you have a problem on one of them. What is different on floors one and two? What is the same?

Info provided will help members here, and you, sort things out. If you can troubleshoot that dryer and lights problem in that other thread you can do this too.
 
Take a breath. You have three floors, you have a problem on one of them. What is different on floors one and two? What is the same?

Info provided will help members here, and you, sort things out. If you can troubleshoot that dryer and lights problem in that other thread you can do this too.

I will look closely tomorrow. The light problem is something I can relate to. The problem I am dealing with is a like a ghost. It is not a constant problem. Just when it feels like. Tomorrow at 6:00 am we are replacing the 75 kva transformer. Hope it fixes it "fingers crossed. We already purchased the transformer a month ago. This transformer has 2.6 amps going to ground "egc" to the 480 panel. At the 208 panel egc I only read .4 amps.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I belive my problem Is harmonics. Just read some info on a site about harmonics. ...
I kind of wish I read this sooner looks like I might need k rated transformers. ...
A K rated transformer does nothing to remove a harmonic problem, if there is one. It just prevents damage to the transformer itself is there really is a harmonic issue.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
...This transformer has 2.6 amps going to ground "egc" to the 480 panel. At the 208 panel egc I only read .4 amps.
Tell us exactly how you took these readings and exactly where you took them. Also, current on the EGC is very unlikely to be caused by the transformer. Most of the time that is caused by neutral to ground connections on the load side of the system bonding jumper.
 
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