Methods of Purifying and Drying Out of Transformer Oil
Q. State the methods of purifying and drying out of transformer oil and explain any one method brief with neat sketch
Q. Explain the filtering process for transformer oil filtration.
Purifying of transformer oil :
There are mainly following three types of oil filter in common use
- Centrifugal purifiers
- Stream line purifiers (filter pack-up)
- Activated earth media : Filter system
The various methods of drying out the machine are as follows :
- External heat
- Internal heat
Centrifugal Purifier :
- Transformer
- Regulating valve
- Strainer
- Pump
- Heater chamber
- Spray chamber
- Centrifugal bowl
- Drain valve
- Vacuum tank
- Vacuum pump
- Discharge pump
- Outlet valve
- The purpose of oil purification is to remove from it all the impurities or all contamination such as water, carbon deposits, dirt, sludge, dissolved moisture and gases so as to improve its dielectric strength and give other properties required.
- Out of the above the centrifugal purifier gives the best result.
- The specific gravity of such impurities is more than the oil.
- In this method the oil is admitted into the center of a bowl having number of conical shaped separating vanes fixed on the vertical shaft.
- The shaft is coupled to a electric motor, which moves at very high speed 6000 to 8000 rpm. This causes high centrifugal forces on the heavier particles in comparison with oil particles.
- This force is thousand times greater than the force of gravity and they are thrown outwards directly to the bowl wall and gets separated from oil.
- When oil is centrifugal at high speeds it leaves the bowl in the form of extremely fine spray due to which evaporation of moisture takes placed and dissolved gases are released.
- If high vacuum is maintained in the spray chamber and oil at high temperature is circulated in the chamber the process is accelerated and can be carried out at high rates.