Transformer Oil

Transformer oil is a mineral (clean hydrocarbon) oil, which is obtained by refining crude petroleum. It has the following purposes:

• It provides additional insulation.
• It carries away the heat generated in the core and the coils.
• It protects the paper from dirt and moisture.

Transformer oil has the following properties:

• High dielectric strength.
• Low viscosity to provide heat transfer.
• Good resistance to emulsion.
• It must be free from inorganic acid, alkali and corrosive sulphur.
• It must have high flash point.
• It must be free from sludging under normal operating conditions.

The most important factors are:

• Operating temperature.
• Atmospheric conditions, particularly inside stations.
• Electric strength.
• Moisture and other contamination.
• Sludge formation.