Bucholtz trip without DGA

[dani864]

We have a Zigzag transformer that had Bucholtz trip probably due problems on external line.
Immediately the customer takes DGA from bottom. The Hydrogen was 14 PPM and other gases also low. No C2H2, C2H4, 5 PPM.
Because this low values the transformer return to service and had another trip. Than it was moved to depot and opened. Inside the upper wood was broken and one of the coils was opened, but no electrical damage or burn signs.
The DGA from oil just before opening was 64 PPM H2 and no other gases more.

How it is possible that Bucholtz tripped from gases and in the same time or even 24 hours after it, they were not dissolved in oil, at least not in the bottom. Unfortunately the client not sample from the Bucholtz itself.

Thanks

 

[ScottyUK]

The Buchholz relay is designed to detect sudden surge in the oil from the tank to the conservator as well as to trap accumulated gases. A flapper hangs down into the oil pipe which will allow gentle flow due to expansion without movement but will operate a microswitch if a sudden disturbance occurs. If the transformer has seen a fault severe enough to cause structural failure within the tank then oil movement is quite possible.


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Sometimes I only open my mouth to swap feet...

 

[dani864]

Thanks for reply
In the Bucholtz were accumulated gases at least 3 times. The transformers owners made the common mistake and told that he release the gases.
I assumed that the gas was probably Hydrogen and I am wonder how it not dissolved in oil
Did some one else experience this phenomenon?