Transformer DGA Results
Transformer DGA Results
(OP)
Hey folks,
So I've been reading lots of presentations/IEEE papers trying to find out the root cause of a transformer failure.
The brand new transformer was commissioned less than a year ago, all protection trip signals for high temperature and low oil levels were wired to a protection relay and commissioned. the temperature and oil level alarms were also wired into a PLC and they don't show any change in state either.
I'm attaching the DGA results screenshot here.
What confuses me is this:
I checked the metering data and there doesn't seem to be any overloading condition in the past few months or even the day the failure occured.
So I've been reading lots of presentations/IEEE papers trying to find out the root cause of a transformer failure.
The brand new transformer was commissioned less than a year ago, all protection trip signals for high temperature and low oil levels were wired to a protection relay and commissioned. the temperature and oil level alarms were also wired into a PLC and they don't show any change in state either.
I'm attaching the DGA results screenshot here.
What confuses me is this:
- The Ratio Tests (Rogers Method/Basic Ratio Method) point to High Energy Arcing Discharge.
- The Key Gas Method points to Electrical High Energy discharge as well, but potentially also a "thermal oil" fault type as well.
I checked the metering data and there doesn't seem to be any overloading condition in the past few months or even the day the failure occured.






RE: Transformer DGA Results
The transformer needs an internal inspection to find out where the arcing fault was there and further to rectify.
Rompicherla Raghunath
RE: Transformer DGA Results
RE: Transformer DGA Results
there is a tap changer, not sure if on-load, but i'm certain its never been used (if that makes a difference).
what are you suspecting?
and what do you think makes it look like a strange pattern? do you typically see gas numbers that tilt 100% in one direction (thermal failure vs electrical failure) as opposed to a mix like what we have?
RE: Transformer DGA Results
RE: Transformer DGA Results
This sample is after the fault occurred? Without a pre-fault DGA, it's very hard to tell why it happened.
How is the condition of the oil?
RE: Transformer DGA Results
If it is a routine test, you may conduct another test after a month or two and compare. If the trend is giving some clue, then act upon.
Just to clean the slate, you have to filter the oil (including the de-gassing). At that time perform the DGA and keep it for the reference. Another reading after two months, would tell you if there is any concern.
RE: Transformer DGA Results
RE: Transformer DGA Results
Hi PRC! would you mind sharing this data? It would be really helpful. Perhaps a dropbox link?
Additionally, I can show you pictures of the fault we are dealing with.
sorry i should have been more explicit in the OP, this was a catastrophic failure on the transformer. it didn't blow up, but internally one of the windings got shattered and lots of bent copper/metal.
RE: Transformer DGA Results
It is basically a diagnostic test.
For a transformer in service, this test gives the clue, that what is happening inside the transformer. Internally the transformer is like a chemical factory. Based on the transformer condition, lot of changes taking place. The gas released during this process, gives a good clue, whether transformer has some in-detectable sparking, discharges or heating up due to some reasons such as overload etc.
It tells you how urgently you have to attend the problem, if it exists.
In your case you know the transformer is already faulty and needs attention. So the DGA would give some clue to the root cause analysis (RAC). But, it may not help much.
When the patient is dead, why you need to conduct the diagnostic tests on the body?
Only the post mortem will be conducted. (Only on a lighter vein, no offense please.)
RE: Transformer DGA Results