arcing noise coming from power transformer 2

[farooquekhann]

On a newly installed power transformer, we are observing some arcing type noise coming from (most probably) the tap changer. The noise is noticed on a single tap only: when the transformer is at some other tap, the operation is noiseless.
Can anyone please point out the reason and remedy for this issue?

 

[marks1080]

The reason could be because the tap changer is arcing. This is potentially a very serious issue. Personally I'd take the unit out of service and begin sampling the oil.

 

[prc]

Find out on which tap the arcing occurs. Verify with the rating and diagram plate. Check whether at this tap the regulating winding is floating. If no tie in resistor is provided, it can happen. Conduct a DGA of main tank oil and LTC chamber oil.

 

[Marmite]

If there is arcing within the tap-changer there is a real possibility of a catastrophic explosion and fire. For your own safety, and that of your colleagues, all of your investigations should be done with the unit de-energised.

Regards
Marmite

 

[prc]

I am not contradicting Marmite's advice. But let me add, all arcs under oil are not that explosive as mentioned esp when source fault level is low and the fault is at the neutral end of winding(as with tap changer)This is the reason why a minor inside fault in transformers in major cities can result in tank rupture and some time a fire. Without tank rupture there will be no fire as without oxygen fire cannot start. But an identical fault in a remote area without much interconnection will lead to a safe tripping out only. After all we were using oil as an arc quenching medium in oil circuit breakers !!

 

[Andiri812]

If the Trafo is small enough and has an OLTC then open it up and take a look... to heck with wasting time on the DGA unless you have a testing lab up the street. Otherwise if its new and under guarantee, get on the blower to the manufacturers and get them to address the issue.

 

[unclebob]

The DGA results will be the proof the manufacturers want. Else, they will tell you there is no problem.
Any news om this one?