Transformer Oil Purification


High Voltage Transformer Maintenance: Oil Purification


Oil is a critical component of high voltage transformers. It acts as a high dielectric insulating material and an efficient coolant. The oil also offers some protection against chemical corrosion and sludge build up.


Transformer oil deteriorates over time. When the properties of the oil change it no longer performs as efficiently. Oil in poor condition may even damage equipment and become hazardous to personnel and the environment.


Regular transformer oil purification will ensure your transformer oil is maintained in good condition. For the best results oil purification should be performed on site with specialist equipment that combines heat vacuuming and coalescing filtration.

How does oil purification work?

Sustainable Energy Design has purpose-built machinery for providing effective oil purification.

  • Vacuum evacuation removes moisture from the transformer oil and paper insulation
  • Combined with heat the vacuum evacuation provides the side effect of degasification
  • Mesh filters capture particles in the transformer oil
  • Liquid level detectors and controls ensure internal components are not exposed

Combining vacuum evacuation and heating offers a high degree of dehydration and degasification leaving your transformer oil dry and free of unwanted oxygen and combustible gases.

SED’s specialist equipment combines double vacuum chamber water and gas extraction with triple particulate filtering. The process can be performed on-line, while the transformer is active, or off-line.

Benefits of On-line vs Off-line Purification

Oil Replacement: Oil purification has benefits over replacing the oil. Changing the oil will result in clean oil but will not remove any sludge adhering to the transformer components.

On-line Purification: On-line vacuum dehydration and degasification is effective in removing moisture and dissolved gases from the insulation oil, and in reducing the moisture content of the paper insulation.

Off-line Purification: Single pass off-line treatment removes the moisture from the oil but not the paper insulation. Off-line processing should be repeated three times to effectively remove moisture from the oil, the windings and the paper insulation.

Safety Assessment: While on-line oil purification is the most effective method of oil purification it is not always a safe option. SED has experienced technicians who will assess the safety of performing on-line purification at your installation. If they do not deem it safe to perform on-line purification they will recommend off-line purification.




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