# Transformer tracking?



## NickPic83 (Apr 26, 2012)

the building i am working in has 4 substations with dry type "Y,Y" transformers in them. 3 of them are 13,200 to 277/480 and the other steps it down to 208/120. on the covers by all the bolts or anywhere the paint is chipped we have burn marks. they have been getting bigger as time goes but they seem to have been getting worse faster now and i see some new ones that are pretty bad. the covers are burnt all around the bolts by about an inch and where the cover meets the enclosure is burnt even more. then were the chipped paint is there is several different sizes but one is as big as say a half a dollar bill

square D came in here a couple years ago to go over all of it which includes re-torqueing, cleaning, checking for proper grounding, and thermal tests. it all checked out and they said the burn marks were tracking due to dirt and spider webs. now i know this is possible but the gear is not that dirty now were it should track faster than it ever has. 

anyone experience this or have any thoughts?


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## Zog (Apr 15, 2009)

Lots of things besides dirt can cause tracking, or more accurately, Partial Discharge. The enclosure acts like a capacitor to transmit TeV (Transient Earth Voltages) to ground when partial discharge is present. I recommend through cleaning by people that know how to clean a transformer right with PD surveys before and after the cleaning. If PD is still present you may have to have the insulation repaired or reconditioned.


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## Big John (May 23, 2010)

Stupid question, are you 100% sure this is due to tracking?

If you have enough current flow to cause burn marks, not only should it be measurable, but there is no way you wouldn't see evidence of tracking and corona on the insulators and bushings. 

My thinking is you're actually seeing a galvanic reaction because of dissimilar metals between the bolts and the transformer body. Are they stainless?


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## brian john (Mar 11, 2007)

I have seen something similar and it was purely dust. Transformers are dust magnets.


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