transformer damage?

[kingpb]

Let me guess, $100M for the 7 units?

Who is making these for you, ABB?

Right around there for the $$. The Owner's preferred manufacturers are ABB (Germany) Areva, Siemens (Croatia), and SMIT (Netherlands)

Shipping wt: approx 420 tonnes (No oil, bushings, radiators etc installed)
60 days for dressing out, filling, and testing at site. They will be going over the road on a heavy hauler from the port to the site.

 

[zog]

You have got to post pictures of that.

I hope they dont look like this..

 

[drbond24]

Preliminary results are in (attached), and they say the transformer got hot. Gee thanks guys, now tell me something I don't already know.

Seriously though, I downloaded IEEE C57.104 and get to spend this morning reading it so I understand some of the stuff on this report a little better.

 

[zog]

Yikes, looks like there is some insulation damage there, you should have this unit tested and the oil processed/replaced. You have an overall condition 4 for the unit on your report, thats not good.

Post any questions you have on that report, here is a chart to help explain what the presence of different gasses means.

 

[drbond24]

What document describes conditions 1 through 4? Our contact at the POCO faxed me a page with the information on it, but I can't find an electronic version of it anywhere. Are these condition ratings specific to Weidmann, or are they listed in a standard somewhere?

IEEE C57.104 says that acetylene is very soluable and disappears after a time. Does anyone know how quickly this happens? There was not an elevated level of acetylene in our sample, but the event occurred 2 and a half weeks before the test. Could the evidence of an arc have disappeared that quickly?

Thanks for the help.

 

[zog]

I have that doc somewhere (1-4) but just changed jobs and need to look for it,

I dont think the gasses can leave that quickly, they need to be absorbed, but I may be wrong about that.

 

[drbond24]

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:

 

[zog]

You had those pics all along? Yep, pretty hot, what are you planning to do next?

 

[drbond24]

We're waiting on full test results and engineering analysis from Weidmann-Acti. We expect them 'early next week' according to our contact at the POCO. Management won't do anything until they have those results and I've already been scolded twice for telling them to replace the transformer so many times, so I'm just monitoring it as closely as possible with the meter we have on the secondary and the infrared camera. It is still working just fine for now.

 

[zog]

Betcha you are going to enjoy when they tell you to replace that baby

 

[drbond24]

I still wouldn't be surprised if they don't replace it. They will probably filter or maybe even change the oil, but I would not be shocked at all at this point if replacement was not on the agenda.

 

[jghrist]

At 34.5 kV, ferroresonance is possible on a grdY-grdY transformer if the ?-? fault was cleared by single phase devises somewhere upstream. The ferroresonance could result in the noises heard and internal arcing.

You probably won't be able to get a definitive cause without tearing the transformer apart for internal inspection.

I've often joked that power engineers blame either ferroresonance or harmonics for any problem that they can't explain otherwise, but I really think that it is the probable cause in this situation. If you tell me that the fault was cleared by a three-phase recloser or the substation breaker, then I'll change my mind.

 

[drbond24]

At 34.5 kV, ferroresonance is possible on a grdY-grdY transformer if the ?-? fault was cleared by single phase devises somewhere upstream. The ferroresonance could result in the noises heard and internal arcing.

You probably won't be able to get a definitive cause without tearing the transformer apart for internal inspection.

I've often joked that power engineers blame either ferroresonance or harmonics for any problem that they can't explain otherwise, but I really think that it is the probable cause in this situation. If you tell me that the fault was cleared by a three-phase recloser or the substation breaker, then I'll change my mind.

I don't know what cleared the original fault. Our transformer wasn't cleared until the POCO manually operated the 3 phase recloser outside our plant. They went down the street out of sight to clear the whole line, so I don't know what they did.

Honestly, this is the first time I can remember hearing the term ferroresonance. I'll try to read up on it and see if our situation fits the conditions.

 

[jghrist]

IHonestly, this is the first time I can remember hearing the term ferroresonance. I'll try to read up on it and see if our situation fits the conditions.

A good place to start is http://www.mikeholt.com/technical.p...erroresonance and Its Effects On Transformers

 

[steveng]

how much $ for a new one?

how much $ for a new one?

I still wouldn't be surprised if they don't replace it. They will probably filter or maybe even change the oil, but I would not be shocked at all at this point if replacement was not on the agenda.

how much is a new one?

what would it cost to the plant if it goes down?



we replaced a 750kva /13.8kv recently. it was about 23k to replace it.

found later we could on got one for 12-16k, cooper also.

sunday we are processing the oil on a 500kva. the actylene readings were.
>800

 

[drbond24]

A good place to start is http://www.mikeholt.com/technical.p...erroresonance and Its Effects On Transformers

Thank you for the link. Something I don't see mentioned that might apply in our case is that there was a capacitor bank (for power factor correction) on the line between the transformer and the fault. The fault was actually not very far from the transformer at all, but with that additional capacitance on the line this becomes more plausible.

how much is a new one?

what would it cost to the plant if it goes down?

we replaced a 750kva /13.8kv recently. it was about 23k to replace it.

found later we could on got one for 12-16k, cooper also.

sunday we are processing the oil on a 500kva. the actylene readings were.
>800

The estimate we have for an emergency replacement if our transformer goes down is ~50k. This is the only transformer on the only power feed into the plant, so obviously without it production dies.

I'm new at this, but that acetylene reading is insanely high! That's a lot of arcing.

 

[zog]

You realize that there is up to a 6 month lead time on some Oil Filled transformers these days right?

 

[drbond24]

The POCO actually has a spare on hand that they can have changed out within 24 hours if need be. The only problem is that our existing transformer (and the aforementioned spare) are 2500 kVA and now we are talking about upgrading to a 3750 kVA. I agree that a larger transformer would be a good idea, but we've been getting lead time estimates of 16 to 18 weeks on a 3750 kVA. I doubt we have that kind of time.

 

[drbond24]

The results are finally in, but the file is too large for me to attach. There really wasn't much extra that wasn't in the DGA analysis already posted. They perfomed a furanic compound test and verified my estimate for aging (I had said that we aged the transformer 7.5 years in 30 minutes due to the heat). Their estimate for age of the unit was 20 years when it is really on 12. :smile:

They recommend that we take another sample in two or three months and compare with this one so we can establish a trend. They didn't sound terribly worried about imminent failure, but that doesn't make me feel much better about it.

The more I read about ferroresonance the more I think that might be what happened. We do meet all of the requirements.

 

[mivey]

The more I read about ferroresonance the more I think that might be what happened. We do meet all of the requirements.

What did the transformer sound like during the event?