Transformer Dissolved Gas Problem ??
Transformer Dissolved Gas Problem ??
(OP)
I have a 60MVA Transformer which has had a DGA carried out as I am switching it out for routine checks in a months time. The analysis looks normal apart from one result. The Ethane content, instead of being around 10 ppm is 42ppm. Should I be worried so early into the life of this 1 year old transformer ?? Any practical guidance welcomed...






RE: Transformer Dissolved Gas Problem ??
Whats the voltages and any faults seen by this txf? Maybe a lead connection inside has loosened.
wbd
RE: Transformer Dissolved Gas Problem ??
Bru
RE: Transformer Dissolved Gas Problem ??
my email is gmazumder@yahoo.com
regards
gautam mazumder
RE: Transformer Dissolved Gas Problem ??
Oxygen 26601.6ppm
Nitrogen 105310.0 ppm
Hydrogen 10.9 ppm
Carbon Monoxide 38.0 ppm
Carbon Dioxide 986.6 ppm
Methane 7.0 ppm
Ethlyene 3.6 ppm
Ethane 3.6 ppm
Acetylene 0.0 ppm
Moisture content 9 ppm
Total Gas in Oil 13.83% CO2/CO 25.09
Thanks to all.
RE: Transformer Dissolved Gas Problem ??
The gas content seams to be normal.
DGA needs to analysis 3 items.
1- the gas content, there are two limits, one minimun for being considered and the upper limits.
2- the gas ratios, using diferent criterias such as Rogers, IEC, Dornemburg, Duval.
3- the trending of the 2 items.
It is not recommended to use only one gas or ratio.
The IEC 60599 is very complete for doing diagnosys.
Also you can use the U.S.B.R. papers.
sincerely
HY
RE: Transformer Dissolved Gas Problem ??
wbd
RE: Transformer Dissolved Gas Problem ??
The Ethane value should have been : 41.9 ppm
All others are correct.
Thanks for the info
fb599
RE: Transformer Dissolved Gas Problem ??
Why do you think the ethane should be ~10?
How many DGA results do you have for this unit, and were they all analysed at one lab?
What is the load history on this unit - full 60 MVA or part load?
Have you any similar units, and what are they doing?
Have you resampled since the worrying result?
DGA is about getting a feel for a transformer's life blood - the oil. But DGA needs to be used carefully - there are risks of both false positives and false negatives. Use as many standard interpretations of levels and ratios as possible to help see what the picture is.
RE: Transformer Dissolved Gas Problem ??
We have a similar unit again one year old that has a 9.4 ppm reading. From what I've learnt in supporting literature below 10-15 is normal. These tests were carried out at the same lab and they are the first tests too for the unit. Loading has been cyclic and not always fully loaded. I'm not sure if I'm worried.....maybe just concerned at the reading and looking for reassurance. Since talking to colleagues on the same network in a different island their readings are up to 200 ppm Ethane for a simiolar units so we are now working together on this one. Thanks fb599
RE: Transformer Dissolved Gas Problem ??
RE: Transformer Dissolved Gas Problem ??
RE: Transformer Dissolved Gas Problem ??
Ethane content usually indicates some overheating at some point; this is something that needs to be trended to get any useful information. A single data point is pretty meaningless.
If you had acetylene, you'd be looking at arcing - much more serious.
RE: Transformer Dissolved Gas Problem ??
RE: Transformer Dissolved Gas Problem ??