Large Restaurant Power Interruptions

Ravenvalor

Senior Member
Hello,

I have a restaurant customer who is experiencing very brief (1 second), intermittent (3 - 4 times per week) total power interruptions. This is occuring throughout the entire restaurant. This started about 4 - years ago however it seemed to stop occuring until about 3 - weeks ago when the problem has started again. The Alarm company said that it had nothing to do with any smoke alarms. The power company put reading devices on the transformer about 4 - years ago. Nobody at the restaurant knows what the POCO discovered or did to correct the problem then. My question is whether or not the main breaker could be causing the problem. It does have a GFCI built into it. Everything at and around the main breaker looks to be in tip top condition. The restaurant is about 16 years old.

Thanks for all of the great advice.....
 

charlie b

Moderator
Staff member
Location
Seattle, WA
Occupation
Electrical Engineer
I think the most relevant thing you said is that the power interruptions are "brief." That means that power was restored without human intervention. So it is not a trip of the breaker or the GFCI feature. To me, this sounds like a loose connection. That, of course, could be anywhere. I am afraid I don't have the background that would enable me to offer any troubleshooting advice. Good luck with this one.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
Instead of guessing you have to do some investigating yourself. Since this is a recurring problem it should be easy to determine where it's coming from. Simple power monitoring equipment is all that's needed. Start on the utility side of the main.

-Hal
 

Ravenvalor

Senior Member
Instead of guessing you have to do some investigating yourself. Since this is a recurring problem it should be easy to determine where it's coming from. Simple power monitoring equipment is all that's needed. Start on the utility side of the main.

-Hal
Thank you for both of the excellent replies. I believe that the POCO will be connecting their monitoring equipment today.
 

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petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I think Charlie is probably on track. I seriously doubt it is anything tripping as that would likely have to be reset.

Most likely it is a loose wire somewhere.

You will need to do some investigation. You may start tightening things up and the problem just goes away and never know what it was.
 

Boerg

Member
Location
Oklahoma City
Occupation
Engineer
My first guess would be that it's on the utility side. If it's an overhead feeder, then reclosing is probably enabled on the substation breaker or a recloser between the customer and the substation. Sometimes bad lightning arrestors, damaged insulators/ties, trees, squirrels, etc can cause recurring transient faults that will blink the entire circuit.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
If they lose all phases on a 3 phase service it's not likely to be a loose wire.

-Hal
good point. the OP though is not clear if they are losing all power or just some.

does not seem likely to be a recloser issue since the OP mentioned power loss was just a second. I don't know how it is where you are but here the reclosers take longer than that to reset.
 

tom baker

First Chief Moderator
Staff member
The original post mentions the main breaker has a GFCI built in to it. Its actually a GFPE. GFCI is for personnel protection and GFPE is for equipment protection. There is a huge difference in the trip level. Must be a large restaurant if it has GFPE, as those are only used on large services.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
If it's all three phases that wink out, that's often indicative of a utility grid switching event; they are moving power from one area to another meaning HV switches somewhere are opening, then others close. It's part of the new "smart grid" getting installed everywhere. In the past these may have been much longer outages, but now they are just blips.

This is an unnecessarilly long video, but it does a decent job of explaining how things work now.
 

Ravenvalor

Senior Member
If it's all three phases that wink out, that's often indicative of a utility grid switching event; they are moving power from one area to another meaning HV switches somewhere are opening, then others close. It's part of the new "smart grid" getting installed everywhere. In the past these may have been much longer outages, but now they are just blips.

This is an unnecessarilly long video, but it does a decent job of explaining how things work now.
Great call Jraef. I watched some of the video.
I can imagine Duke Energy not telling the customer that the problem is an utility grid switching event.
If this was the case it seems that this problem would be affected by the restaurant's neighbors? I will check.
Also, to answer other questions.
The customer confirms that the power is complete restaurant wide.
It is an underground service.
Thanks,
 

hillbilly1

Senior Member
Location
Atlanta,Ga
The original post mentions the main breaker has a GFCI built in to it. Its actually a GFPE. GFCI is for personnel protection and GFPE is for equipment protection. There is a huge difference in the trip level. Must be a large restaurant if it has GFPE, as those are only used on large services.
And 480 volt......
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
If it's all three phases that wink out, that's often indicative of a utility grid switching event; they are moving power from one area to another meaning HV switches somewhere are opening, then others close. It's part of the new "smart grid" getting installed everywhere. In the past these may have been much longer outages, but now they are just blips.

This is an unnecessarilly long video, but it does a decent job of explaining how things work now.
Depending on where your at they could be ”blips” or blinks.
our recloser are set on 1 second, 5 second, and 15 seconds Recloser intervals.

if it is a one second blink and then all is well for a while, I’m looking for a bad arrestor. Especially if it does this every time it rains or heavy dew mornings.
if it gets through two or three blinks, it’s out, unless there is some communication with self healing in place.

theres a couple of different ways do do self healing schemes.
one is communication assisted where the relays are in constant contact with one another. When one senses a fault that opens a recloser, then the system sectionalizes the line and restores power to as many as possible.

another way is time based. This is where communication isn’t used, but rather the logic is looking for a time signature in the recloser times to determine the fault location. These types of schemes are very good, but the downfall is the time it takes to restore power. For this type of scheme the self healing time is around 45 seconds to a minute.

we have the time based scheme and the logic we came up with looks for an 8.5 second, or 12.5 second blink before self healing initiates. We took out fast curves and used slow curves only. If it doesnt clear with two shots, chances are it isn’t going to clear.
 

Jraef

Moderator
Staff member
Location
San Francisco Bay Area, CA, USA
Occupation
Electrical Engineer
In my experience when people say "the power went out for a second and came right back on", it's rarely "a" second; they are not using a stopwatch. They generally just mean "not very long"...

A few years ago I had a customer that was losing VFDs right and left, all different brands, sizes etc. We had a couple of other customers in the same general area with line recording systems installed that gave us access via the web. It turned out we could directly correlate their VFD failures to transient events on the utility side. They installed line reactors and their troubles went away. The most shocking thing however was that on some of those days, they had upward of 20 grid transients per DAY. These systems have improved overall reliability, but have increased the number of transients from when those switches open and close.
 
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hillbilly1

Senior Member
Location
Atlanta,Ga
I had a Church complaining of the same thing a couple of years ago, Met with Georgia Power, they said they would put a power monitor on the transformer. We also put one one the main gear. Two days latter, the maintenance guy said he saw a bunch of line trucks working up and down the road the next couple of days. The blips quit after that, but Georgia Power did not admit that the problem was on their end. The substation was not too far away.
 

Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
In my experience when people say "the power went out for a second and came right back on", it's rarely "a" second; they are not using a stopwatch. They generally just mean "not very long"...

A few years ago I had a customer that was losing VFDs right and left, all different brands, sizes etc. We had a couple of other customers in the same general area with line recording systems installed that gave us access via the web. It turned out we could directly correlate their VFD failures to transient events on the utility side. They installed line reactors and their troubles went away. The most shocking thing however was that on some of those days, they had upward of 20 grid transients per DAY. These systems have improved overall reliability, but have increased the number of transients from when those switches open and close.
We have a sawmill right now causing havoc on one of our circuits because of some very large motors they added. (300horse apiece) .
ive had monitors on their transformer for two days now. When I first set it up I measured PF at 59%...
 

Ravenvalor

Senior Member
The restaurant management informed me today that the POCO detected a defective component on their end, possibly at the transformer. They told him that it was a PMH-9 switch. Since they repaired the problem the restaurant has not experienced any power blips. Thanks for all of the great help with this problem. Your assistance is priceless.
 
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Hv&Lv

Senior Member
Location
-
Occupation
Engineer/Technician
Kind of odd since that is an UG fuse cabinet, but whatever... as long as its fixed.
 
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