Message Board Thread - "Transformer Unusual IR profile"

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Transformer Unusual IR profile bnice711 3/16/2009
The following IR image was taken of a high voltage transformer. We believe there is internal failure/arching creating the image. The temperature varies with the load applied. But the customer believes this is a normal IR images. I would like any comments dealing with this image.
 
Re:Transformer Unusual IR profile Bob Berry 3/16/2009
Suggest you get some DGA done on the transformer.
 
Re:Transformer Unusual IR profile Mr. G 3/16/2009
Bruce,
Like Bob Berry suggests below, get a DGA done. If you need more info about DGA let me know. If the DGA comes back with gassing, then you may want to have a PD test done. I can help with that as well. www.powerpd.net
I have seen this type of heating many times. You should switch to using "C" so you can do a gauge check and know how your cooling system is working. Your range is 28 to 51 C....A 20 C delta hot spot (above top oil) is worth looking into.

Jon Giesecke
JLG Associates LLC
610 518-1656
 
Re:Transformer Unusual IR profile dmucklejr 4/2/2009
Mr. G wrote:

Like Bob Berry suggests below, get a DGA done. If you need more info about DGA let me know. If the DGA comes back with gassing, then you may want to have a PD test done. I can help with that as well. www.powerpd.net
I have seen this type of heating many times. You should switch to using "C" so you can do a gauge check and know how your cooling system is working. Your range is 28 to 51 C....A 20 C delta hot spot (above top oil) is worth looking into.

Jon Giesecke
JLG Associates LLC
610 518-1656
Agree 100% with Jon's recommendations. Oil sampling of the xfmr will tell the tale. I have never seen this and would like to know the outcome.

Denny Muckle
Senior Testman
Groton Utilities
 
Re:Transformer Unusual IR profile dan roark 4/2/2009
I'm not familiar with the manufacture of this unit, but I have had a simalar image. It was of a 66KV/13.8KV distribution transformer. I too suggest DGA.
What we found was a secondary core ground, allowing the iron in the structure to carry a limited amount of load current.
We resolved that this "may" be because of winding insulation breakdown. We're not sure and this is speculative because the tank is too tight for our maintenance crews to make internal repairs. The transformer is somewhat old. In the range of 50-55 years. We did eliminate the problem using high current testing, but as soon as the unit was re-energized, the ground re-established.
At this point, we continue to monitor periodically for significant change.
Hope this helps. Good luck.

Dan Roark
Knoxville Utilities Board
 
Re:Transformer Unusual IR profile DWA 4/2/2009
dan roark wrote:
familiar with the manufacture of this unit, but I have had a simalar image. It was of a 66KV/13.8KV distribution transformer. I too suggest DGA.
What we found was a secondary core ground, allowing the iron in the structure to carry a limited amount of load current.
We resolved that this "may" be because of winding insulation breakdown. We're not sure and this is speculative because the tank is too tight for our maintenance crews to make internal repairs. The transformer is somewhat old. In the range of 50-55 years. We did eliminate the problem using high current testing, but as soon as the unit was re-energized, the ground re-established.
At this point, we continue to monitor periodically for significant change.
Hope this helps. Good luck.

Dan Roark
Knoxville Utilities Board
I have seen this in several instances and agree with the DGA test first. I would also be curious as to what is physically behind that wall at that heating spot. I would try to locate a drawing of the inside of that transformer. This heating spot could possibly be a structures support for the windings? Could be an additiional core ground allowing circulating current. Could also be a core booster winding or a preventative auto winding for the LTC. Did you happen to change taps to see of there was any change in temp?
 
Re:Transformer Unusual IR profile ggeneral 4/7/2009
If you have disolved gases, look for acetylene, the result of arcing, with other gases present just due to heating. Another possibility, is there a tap changer in this transformer?? Sometimes moving the tapchanger can improve the contact area and possibly eliminate the problem.
 


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