How to Test for Partial Discharges in Power Transformers

The transformer manufacture should have a partial discharge tester.
Can you return the transformer to the manufacture and have him test it.

We used to test transformers for partial discharge using document MIL-T-27C. The current version is MIL-T-27E?
This test is not as simple as shown in MIL-T27 and requires more equipment than indicated in MIL-T27.
There used to be a source where MIL-T-27 could be obtained for free.

An AM radio tuned to a quiet spot can also be used to detect partial discharge.

Another name for partial discharge is corona.

Hi Carl.

Thanks for take part of you time for help me, Regarding you answer, we have this unit out of service and we have it in the backyard, because the HV side is in 69 KV we don't have how connect it, thats what I need is to know a way to test it without be energized.

Thanks again for you support.

Regards Mario

If you already did all of the tests you listed at your site and did not find signs of corona internally (assuming you did a thorough internal inspection), then there is little more you can do without sending it to the manufacturer for them to investigate. Corona inside a transformer can be difficult to track down.

There is another possible source of hydrogen generation in the transformer oil. If you have moisture in the oil (and there is always some ppm water), and during manufacture someone accidentally used some galvanized parts (maybe bolts / nuts), it is possible to get hydrogen by hydrolysis of the water. The zinc in the galvanizing acts as a catalyst for the reaction. If it is still possible to do further internal inspection, look for someplace where instead of bronze or copper hardware, galvanized was used.

Also look at the contact surfaces and the contact pressure of the DETC (de-energized tap changer) - often the contact pressure is low, so there is some heating of the contacts that is enough to generate hydrogen but not much other gases.

Dear Peter.

Regarding you commentaries about the Pd's, I still with the problem and looking for the solution, I try to contact the Factory of this unit but till now no body answer because they change to ABB, and is to sad keep this unit in the yard when is almost new, I saw inside and not fund any galvanized component, but abour the DETC do you know what's the pressure that this device need in PSI, or other parameter of pressure.

Thanks for you kind attention and support.

Mario