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You would be aware that transformer has an insulating oil, which oil is that?
When such type of transformer interview questions are asked, you need to say that highly refined mineral oil is mostly considered as transformer oil or insulating oil as it is stable at high temperatures and good electrical insulating properties. Elaborate on the properties of the oil a?
INSULTING PROPERT? This is a very important property. However most of the oils naturally fulfill this. Therefore deterioration in insulating property due to moisture or contamination may be more relevant.
VISCOSIT? It is important as it determines the rate of flow of the fluid. Highly viscous fluids need much bigger clearances for adequate heat removal.
PURIT? The oil must not contain impurities which are corrosive. Sulphur or its compounds as impurities cause formation of sludge and also attack metal parts
SLUDGE FORMATIO? Thickening of oil into a semisolid form is called a sludge. Sludge formation properties have to be considered while choosing the oil as the oil slowly forms semi-solid hydrocarbons. These impede flows and due to the acidic nature, corrode metal parts. 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
ACIDIT? 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 POIN? 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?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?C)
Inhibited oils and synthetic oils are therefore used in the transformers. Inhibited oils contain additives which slow down the deterioration of properties under heat and moisture and hence the degradation of oil. Synthetic transformer oil like chlorinated di-phenyl has excellent properties like chemical stability, non-oxidizing, good dielectric strength, moisture repellent, reduced risk due fire and explosion.
It is therefore necessary to check the quality of the oil periodically and take corrective steps to avoid major break downs in the transforme .
INSULTING PROPERT? This is a very important property. However most of the oils naturally fulfill this. Therefore deterioration in insulating property due to moisture or contamination may be more relevant.
VISCOSIT? It is important as it determines the rate of flow of the fluid. Highly viscous fluids need much bigger clearances for adequate heat removal.
PURIT? The oil must not contain impurities which are corrosive. Sulphur or its compounds as impurities cause formation of sludge and also attack metal parts
SLUDGE FORMATIO? Thickening of oil into a semisolid form is called a sludge. Sludge formation properties have to be considered while choosing the oil as the oil slowly forms semi-solid hydrocarbons. These impede flows and due to the acidic nature, corrode metal parts. 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
ACIDIT? 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 POIN? 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?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?C)
Inhibited oils and synthetic oils are therefore used in the transformers. Inhibited oils contain additives which slow down the deterioration of properties under heat and moisture and hence the degradation of oil. Synthetic transformer oil like chlorinated di-phenyl has excellent properties like chemical stability, non-oxidizing, good dielectric strength, moisture repellent, reduced risk due fire and explosion.
It is therefore necessary to check the quality of the oil periodically and take corrective steps to avoid major break downs in the transforme .