Things To Be Consider Before Transformer Oil Filtration

There are things to be consider before begin any oil filtration process for the transformer. You can conduct transformer oil filtration once you complete the process and perform all the tests to ensure the right time for energizing the transformer device. You should never energize the transformer without performing these tests and checks.


Just in case any of the tests mention below fail and transformer is energized, you may end up with serious issue that will not be good for your transformer health. So, read these tests and ensure proper checks before starting energizing of the transformer.

  • Insulating fluid test

Take a sample fluid and test its dielectric strength, which should be minimum 26 kv or more.

  • Pressure test

Look for leakage in transformer tank using pressurizing method. Pressurize the tank with dry air or dry nitrogen using pressure test fitting at 3-4 PSIG pressure. Let it stand under pressure for minimum one hour to two hours and then check the tank and its fittings and look for leakage points. You can easily detect the leaks by applying soap solution to all joints, welds, cable connections, and pipe fittings.

You can later reduce the pressure to 1-2 PSIG once you are done with this test.

  • Ratio test

You need to do ratio test to ensure that the coil ratios and tap changer connections in transformer are correct. For this test, you must call experts who will use specialized tools and technology to perform ratio test of transformer.

  • Test continuity and resistance

Perform a continuity and resistance test on every winding of the transformer. Once you measure the winding resistance, compare the results with factory test values. 

  • Ensure tap changer setting

Check the tap changer setting in order to make sure that it is set to the proper position as per the required voltage.

  • Grounding 

You must check and ensure about the grounding of the transformer tank. It should be permanently and successfully grounded.

  • Fasten the loose connections 

Look for loose connections and fasten them if you don’t want to make damage to insulation.

  • Check finish 

Make sure the surfaces of the tank are painted well so that transformer will remain untouched by rust or corrosion.

  • Bolted connections

Make sure all the bolted connections are tightened.

  • Tools

Check and ensure all the tools and equipments are accounted for and have been ejected from the system.

These are the obligatory tests and checks that one should perform prior starting transformer oil filtration process. A lot more tests are there to perform; you can find them in the manual shared by your manufacturing unit.