Transformer Faulty - Fault Shown is "TR GAS"

Hi

What are the measured values ie HT to ground, HT to LT, LT phase to ground.

You heated the LV terminals? All you are going to do by doing that is damage the LV bushings where they enter the tank.

I take it you tested the LV terminals to earth, did you disconnect the neutral / earth link first?

Get an engineer in that knows what they are doing before you cause more problems.

(Got to admit though disconnecting the alarm is a sure fire way of getting it to go away)

I agree with TonyS - you need to have someone qualified test the transformer for what caused the gas. The usual culprit is an internal arcing fault of some sort. On a transformer that small, that's the only thing likely to trip a fault pressure relay (educated guess here of what detected the gas).

If insulation resistance really is zero ohms, your winding is shorted to ground, unless you left the neutral link on a wye-connected winding in place. That just doesn't go away on its own. This transformer may be toast.

A big thank you to everybody,i just checked out the transformer and realized the windings are shorted to ground.Anyway, i have taken a sample of the oil to send to a more qualified engineer to examine; but from physical inspection the transfromer oil has been contaminated. Thanks

Yes, the oil is probably contaminated, but that is not the real problem. Whatever caused the contamination (in this case, the winding fault) is the problem. That will probably require detanking the transformer core & coils for inspection and rewinding. Depending on the time and cost of that, you may find it is more economical to buy a replacement transformer.

The best that the oil analysis can do is suggest the nature of the fault, and I'm expecting if the winding is shorted it will show arcing products (acetylene, ethylene, plus carbon soot and metal particles).

Low oil level can give transformer gas alarm if the level falls below the Buchholtz float. It would be ironic to have a transformer out of service for 4 months for the sake of a few gallons of oil.

carefull with this. I've seen a lot of transformer damaged caused by insulation failure. The pressure switch and buccholz often indicates an insulation failure. The megger test is already a good indication that there is an insulation failure.

Do you have a TTR (Transformer Turns Ratio tester)? This is a very good tool in checking if you have a turn-to-turns short. Also, a DGA will help you which part of the transformer failed.

Dant