Maintenance Of Transformer Oil

Maintenance Of Transformer Oil

A mineral-based oil, transformer oil, is used for its chemical properties as well as dielectric strength. The oil inside your transformer acts as both an insulator, and a cooling agent. The oil can become contaminated over time and cause costly repairs as well as faults.

This contaminated oil needs to be removed and disposed of properly. This can be done by hiring services for transformer oil disposal via

The schedule of transformer oil maintenance oil type transformer maintenance -

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You can avoid costly downtime and costly repairs by following a preventative maintenance program.

Oil Quality 

Your transformer oil’s quality will affect its insulation and cooling properties. Normal operating conditions will result in a very small amount of oil quality loss due to oxidization or contamination. These can be summarized as:

  1. When oil comes into contact with oxygen, oxidization occurs. Sludge will build upon the transformer windings, resulting in decreased heat dissipation. As the windings heat up, more sludge will form. Increased temperatures and high acidity will accelerate the degradation of the oil’s insulation properties. If left untreated, the transformer will fail.
  2. Water and particulate are two common contaminants found in transformer oil. These contaminants can reduce the insulation properties of your transformer oil.


Your annual preventative maintenance program should include testing your transformer oil. The oil can be tested to determine if corrective actions are needed. The initial testing will provide a baseline for comparison, and the annual testing will show any internal changes in your transformer.

This 4 part test is the minimum requirement for an annual maintenance program.

  1. Dielectric breakdown: This is the voltage that oil will resist. The dielectric breakdown is lower because many contaminants conduct electricity more effectively than oil.
  2. Acid Number/Neutralization: This test measures the amount of sludge that causes acid to be present in the oil.
  3. Interfacial tension: It is a test that detects the presence of polar compounds. These could indicate oxidation of contaminants or deterioration of the transformer materials. i.e. paint, varnish, paper.
  4. Color: The oil’s colour indicates its quality, age, and presence of contaminants.
Hayden Powlett