The schedule of transformer oil maintenance oil type transformer maintenance

oil type transformer maintenance

The frequency of transformers maintenance depends on the importance, design features and durability of transformers. The first step towards a preventive maintenance program is testing. Testing helps us to determine when a treatment is necessary.


Transformer oil is an insulator between the metal parts of the transformer and the wiring within the tank. Over time, the oil can be contaminated with moisture or create combustible gases. By sampling and testing that oil, we can plan repairing or replacing the transformer before a failure occurs.

Maintenance Schedule for Oil Filled Power Transformers

Maintenance or Test

Recommended Interval



Transformer physical inspection



Leakage of oil and reading of MOG (Magnetic Oil Gage) of tanks


In case of unsatisfactory oil level in the MOG, oil to be filled in transformer and also the transformer tank to be checked for oil leakage. If oil leakage is found take required action to plug the leakage. If silica gel becomes pinkish, it should be replaced.


Dielectric strength test (BDV) and moisture content (PPM).



A dielectric strength is a measure of the voltage which is conducted by the transformer oil. At times it is the presence of contaminants which conduct electricity faster than the oil which in turn lowers the dielectric breakdown voltage

Neutralization test



This test which is carried out to ascertain the level of acid which is present in the oil. When oxidation occurs in the transformer oil, it leads to build-up of acid.

Dissolved Gas Analysis Test (DGA)

Annually for 132 KV transformer, once in 2 years for the transformer below 132 KV transformer and in 2 years interval for the transformer above 132 KV transformer.


It helps to analyze the gases which are present in the transformer oil.

Bushings– check of oil level



If it is required, the oil to be filled in the bushing up to correct level. Oil filling to be done under shutdown condition.


Bushings –visual inspection



Bushings – visual inspection and cleaning


5 years

Interfacial tension test

This is a test which is carried out to detect the presence of polar compounds such as paint, varnish and paper.

Tan & delta test

One in two years

Finally the presence of water too is measured as water can decrease the dielectric breakdown voltage of the transformer oil

Colour test

This test indicates aging, quality and the presence of contaminants in the transformer oil.

Transformer excitation current test


5 years

Insulating oil   – DGA, physical,

and chemical tests



Top oil and winding thermometer




Oil level indicator operation


5 years

Sudden pressure relay

5 years

oil type transformer maintenance

oil type transformer maintenance

So, for getting high performance and long functional life of the transformer, it is desired to perform various maintenance activities. GlobeCores’s oil reclamation equipment will keep your transformer oil in the best condition, providing with oil degassing, water and solids removal as well as acids reducing. It’s a fantastic transformer life!