If ferroresonance is the cause, wouln't you expect that the core heating would be indicated in the infrared photos that you took ? I am a total newb on this stuff, but I coudn't find online a picture of a transformer undergoing ferroresonance. My brain would just expect that the RLC ckt formed would make the transformer core look something like a stove heating element, but your pics seem to show arcing at the lugs and possibly xo ? It would be interesting if someone with experience could elaborate on this.
transformer damage?
- Thread starter drbond24
- Start date
- Status
drbond24
Senior Member
- Location
- Barboursville, West Virginia
mivey said:
It was buzzing quite loudly.
nakulak said:
The ifrared camera is only looking at the surface temperture. It can't see 'through' the transformer shell. Yes, there were hot spots corresponding to the lugs and one at the back of the windings, but even the 'cold' spots in those pictures are 400 degrees F.
drbond24 said:
What I hear when reading that is they hope in two or three months you'll be less upset about this event and won't be so insistent on them replacing the transformer. But then, I'm not very trusting of strangers when I think they owe me money.
Oh my, what the pics tell...
Oh my, what the pics tell...
Those hot spots look like internal arcing and most likely permanent and serious damage to the "C" phase windings.
The unit may survive for now, but your next outage will most likely be its last one. (This based on the fact that when de-energized, any contaminants in the oil will settle to the bottom of the tank as the oil cools, and when the power comes back up, BOOM!!)
Some years ago in my very neighborhood a small plane made an emergency landing on a nearby street, taking out a padmount. After the power was restored several hours later, two other transformers in the area failed violently, setting some building's services on fire. (I talked to a poco lineman who was involved, he explained that the two tx's that failed were older, were found to have high contamination of oil and suffered internal arcing that caused the fires by impressing excessive voltage from the 4kv primary on the secondary laterals.)
Take advantage of the poco's spare for now, worry about the upgrade later.
Oh my, what the pics tell...
drbond24 said:Still nothing exciting to report. Awaiting final report from lab next week. I did contact the manufacturer (Cooper Power) and ask them about it. They said that the temperature of the oil would have exceeded the temperature of the tank by 50 degrees C, so we're up to around 650 degrees F on that oil. It got a little warm. Cooper said the insulation will be charred and we should replace the unit. :smile:
For your viewing pleasure, here are the infrared pics I took during the event:
This is the whole transformer about 20 minutes into the event:
After picking out those hot spots on the bottom and rear, I zoomed in on them a little after another 10 minutes or so:
Those hot spots look like internal arcing and most likely permanent and serious damage to the "C" phase windings.
The unit may survive for now, but your next outage will most likely be its last one. (This based on the fact that when de-energized, any contaminants in the oil will settle to the bottom of the tank as the oil cools, and when the power comes back up, BOOM!!)
Some years ago in my very neighborhood a small plane made an emergency landing on a nearby street, taking out a padmount. After the power was restored several hours later, two other transformers in the area failed violently, setting some building's services on fire. (I talked to a poco lineman who was involved, he explained that the two tx's that failed were older, were found to have high contamination of oil and suffered internal arcing that caused the fires by impressing excessive voltage from the 4kv primary on the secondary laterals.)
Take advantage of the poco's spare for now, worry about the upgrade later.
Bumpa bumpa...
Bumpa bumpa...
Bumping this thread up to find out from drbond24 what if any developments have happened since this incident....
Did you get the POCO to install the pole disconnect?
How about the transformer? Poco's spare or is your plant getting a new one?
Would be most unfortunate to have a follow up report be about the violent failure of this transformer...
Bumpa bumpa...
Bumping this thread up to find out from drbond24 what if any developments have happened since this incident....
Did you get the POCO to install the pole disconnect?
How about the transformer? Poco's spare or is your plant getting a new one?
Would be most unfortunate to have a follow up report be about the violent failure of this transformer...
drbond24
Senior Member
- Location
- Barboursville, West Virginia
So far we have still done nothing but talk. We finally did receive approval to replace the transformer, but now everyone has to discuss what size and how to do it and 847 other things that I could tell them in 5 minutes but they won't believe me (ok, I'm ranting a little).
We are getting quotes from all over for 2500, 3000, and 3750 kVA transformers. The last one should be in today or early next week, so maybe pretty soon we'll actually pick one and place an order. In the meantime, we're still using the same transformer that got cooked. Amazingly, we have had no power disruptions since the day of that last event.
We are getting quotes from all over for 2500, 3000, and 3750 kVA transformers. The last one should be in today or early next week, so maybe pretty soon we'll actually pick one and place an order. In the meantime, we're still using the same transformer that got cooked. Amazingly, we have had no power disruptions since the day of that last event.
mxslick said:
Thanks for the update, hope all goes well and if you can, get some pics during the trade-out. 
This caused me a bit of concern though:
"I told them that if we had even had a $400 hot stick we could have saved the ~$80k we're talking about now (because we could have just disconnected the transformer), but they still aren't convinced so far."
If you were thinking of this idea to open the individual fuse cutouts one at a time, that could be more dangerous than letting the transformer cook.....lineman have told me horror stories of flashovers while trying to open cutouts on faulted equipment. And if you haven't practiced how to pull open a cutout quickly, you can easily draw an arc that can create a huge explosion. (That I have seen firsthand, and it's very ugly.) Edited to add: Search Youtube, there are a lot of cutout arc videos.)
That's why I had suggested the switch, it will open all three phases at the same time and is usually rated to open safely under a fault condition. And the mechanism (depending on design) will open fast no matter how slow the operator pulls the handle.
Ain't HV power fun? :grin:
This caused me a bit of concern though:
"I told them that if we had even had a $400 hot stick we could have saved the ~$80k we're talking about now (because we could have just disconnected the transformer), but they still aren't convinced so far."
If you were thinking of this idea to open the individual fuse cutouts one at a time, that could be more dangerous than letting the transformer cook.....lineman have told me horror stories of flashovers while trying to open cutouts on faulted equipment. And if you haven't practiced how to pull open a cutout quickly, you can easily draw an arc that can create a huge explosion. (That I have seen firsthand, and it's very ugly.)
Edited to add: Search Youtube, there are a lot of cutout arc videos.)That's why I had suggested the switch, it will open all three phases at the same time and is usually rated to open safely under a fault condition. And the mechanism (depending on design) will open fast no matter how slow the operator pulls the handle.
Ain't HV power fun? :grin:
Preferably, get the utility to change the protection from fuses to a 3-phase device. This would prevent ferroresonance from occurring for a fuse blowing or when energizing or deenergizing the transformer. At a minimum, I would get a primary switch built into the new transformer so that it can be energized or deenergized without single phasing. This might not have helped the previous case because it was some other device that opened the circuit. If the protection were changed to a 3-phase interrupter, it could be tripped by the same relay that opened the low side breaker. If all you had was the built-in primary switch, I don't think I would want to be the one assigned to open it during another event like the last one.
drbond24
Senior Member
- Location
- Barboursville, West Virginia
An update for those that are interested:
We ordered a new transformer a while back from the POCO. They are going to supply it and install it. It is due to arrive in early September, so in the meantime we're still riding on the transformer that had a problem. It is still operating normally as far as I can tell. We've had a few sags and surges here recently due to thunderstorms and nothing drastic has happened to the transformer during those events.
We also decided to upgrade a bit since we were buying a new one anyway, so the new one is a 3000 kVA while the existing one is 2500 kVA. We have a 4000 A main breaker on the building, so the new transformer will come closer to matching our maximum load.
We ordered a new transformer a while back from the POCO. They are going to supply it and install it. It is due to arrive in early September, so in the meantime we're still riding on the transformer that had a problem. It is still operating normally as far as I can tell. We've had a few sags and surges here recently due to thunderstorms and nothing drastic has happened to the transformer during those events.
We also decided to upgrade a bit since we were buying a new one anyway, so the new one is a 3000 kVA while the existing one is 2500 kVA. We have a 4000 A main breaker on the building, so the new transformer will come closer to matching our maximum load.
zog
Senior Member
- Location
- Charlotte, NC
Thanks for the update, a refreshing change from the posts that never get resolved.
You coudnt get one until September?? We would have had that baby installed weeks ago
Good call on the upgrade, dont forget to redo you PDC, S/C, and arc flash studies. Everything will change.
You coudnt get one until September?? We would have had that baby installed weeks ago
Good call on the upgrade, dont forget to redo you PDC, S/C, and arc flash studies. Everything will change.
Big thumbs up...
Big thumbs up...
...and also as Zog said, thanks for the update.
Try to get some pics during the changeout..oh, and will the POCO be installing that disconnect switch for you?
A primary switch built into the transformer as suggested would be ok, but it brings on it's own hazards, such as having to open the access door on the transformer and having to use a hotstick to operate, but it would definitely be better than having no disconnecting means at all.
Big thumbs up...
...and also as Zog said, thanks for the update.
Try to get some pics during the changeout..oh, and will the POCO be installing that disconnect switch for you?
A primary switch built into the transformer as suggested would be ok, but it brings on it's own hazards, such as having to open the access door on the transformer and having to use a hotstick to operate, but it would definitely be better than having no disconnecting means at all.
drbond24
Senior Member
- Location
- Barboursville, West Virginia
zog said:Thanks for the update, a refreshing change from the posts that never get resolved.
You coudnt get one until September?? We would have had that baby installed weeks ago
That was actually one of the better lead times we were quoted. The only way to get one quicker was to buy a re-constructed one.
zog said:
Thanks for the advice. It was actually a hard fight to convince them to upgrade because it was a little more money than slapping in an equal unit.
mxslick said:
I'll definitely get pictures and post a few of them.
The disconnect is a whole different story. I've argued about that all the way up to the VP of manufacturing, but we aren't getting one. I can't even get a $400 hot stick in case it happens again. I've pointed out that a hot stick would have saved us the thousands of dollars we're spending now, but they don't listen. There must be some stuff going on that I'm not aware of because it seems pretty simple from where I'm sitting.
- Status