You would have to collect a sample and send to a lab to be tested.
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If you have a large power transformer that is leaking oil, do NOT touch it! Older transformer oil contains PCB's which are extremely toxic!! Get a licensed firm to test the oil for PCB's and repair or replace the transformer. Don't fool around with this! PCB's are a serious danger to you and others. Do not let this go. Get it fixed right away!
Transformer oil is pure insulating oil.
The transformer will have to be taken out of service, and topped up. Usually, this would also be a good opportunity to test the oil for contaminants.
why need dielectric test for transformer
An Oil Dielectric Strength Tester is the standard for qualifying Transformer Oil. Thermal Stability would involve heating and then testing. I do not know of a product which controls heat and applies the HV test.
to cool a winding of transformer and it is a insulating material and transformer oil is a purifing oil
On installed transformer a test is performed to check weather it has any oil leakage or not, the test is called pressure test, more precisely pressure leakage test.
open circuit & short circuit test, insulation resistance test, turns ratio, efficiency, if it is oil cooled then breakdown voltage of oil, voltage regulation and definitely visual inpection...
Nytro libra is an uninhibited transformer oil
Short circuit test and open circuit test are widely used to test the efficiency of the transformer.
An oil transformer is filled with PCB oil to better transfer heat from the windings to the outside case (and into the air).
During maintenance following test to be done : transformer oil test ht / lv side insulation test also hv to lt oil temperature trip / alarm winding temperature trip / alarm bukkhoze relay trip / alarm PRV setting to ok MOG trip / alarm etc.