INSULATING PROPERTY:-

This is a very important property of transformer oil. This is stable at high temperature and has excellent electrical insulating properties. However most of the oils naturally fulfill this. Therefore deterioration in insulating property due to moisture or contamination may be more relevant.

VISCOSITY:-

It is important as it determines the rate of flow of the fluid. Highly viscous fluid need much bigger clearances for adequate heat removal.

PURITY:-

The oil must not contain impurities which are corrosive. Sulfur or its compound as impurities cause formation of sludge and also attack metal parts.

SLUDGE FORMATION:-

Thickening of oil into a semisolid form is called a sludge. Sludge formation properties have to be consider while choosing the oil as the oil slowly semi-solid hydrocarbons. Heat in the presence of oxygen is seen to accelerate sludge formation. If the hot oil is prevented from coming into contact with atmospheric air sludge formation can be greatly reduced.

ACIDITY:-

Oxidized oil normally produces CO2 and acids. The cellulose which is in the paper insulation contains good amount of moisture. These form corrosive vapors. A good breather can reduce the problems due to the formation of acids.

FLASH POINT AND FIRE POINT:-

Flash point of an oil is the temperature at which the oil ignites spontaneously. This must be as high as possible (not less than 160 degree C from the point of safety). Fire point is the temperature at which the oil flashes and continuously burns. This must be very high for the chosen oil (not less than 200 degree C).


*This oil also used in high voltage capacitors, fluorescent lamp ballast, and some type of HV switch-gear.