Properties of Good Transformer Oil
Q. State and explain any four properties of good transformer oil.
The properties of good transformer oil or mineral oil are recommended by IS 335-1963. To maintain the properties. IS 1866-1961 is referred. Usually mineral oil grade B is used for switchgears, transformers. It should posses the following properties :
- Water content : The presence of moisture reduces the dielectric strength oil. Water conic should not be more than – 5 ppm.
- Acidity : Acid and present in the old is very harmful. For good insulating oil the acidity neutralization value should be 0.03 mg KOH/gram.
- Density : As per the density at 20°C should equal to 0.89 gm/cm3.
- Flash point : It is temperature at which vapour above an oil surface ignites spontaneously termed as flash point. Flash point should into be less than 160°C.
- Fire point : This is the temperature at which the oil will ignite and continue burning Fire pot should be about 200°C.
- Purity : It should not contain impurities such as sulphur and its compounds. It causes corrosion of metal parts and accelerates formation of sludge.
- Viscosity : Viscosity indicates fluidity, oil with lower viscosity has more fluidity and gives more cooling effect. It can be pass through winding and take heat from it.
- Dielectric strength : The dielectric strength oil should be greater than 30 kV with 2.5 mm standard gap. The presence of moisture reduces the dielectric strength. The oil should fillers periodically and transformer oil should be conditioned.
- Sludging : Sludging means the slow formation of semi-solid hydrocarbons. They block the passage of cooling oil. When the bright copper surfaces are exposed to oxygen the process of sludging accelerate. The remedy is to use a which will not contain sulphur of its component. sludging accelerate. The contact of copper surfaces with any sen should be avoided by providing conservator tank.