Correct Answer - Option 3 : To provide insulation and cooling
Transformer cooling:
The cooling of a transformer is the process of dissipation of heat developed in the transformer to the surroundings. The losses occurring in the transformer are converted into heat which increases the temperature of the windings and the core. In order to dissipate the heat generated cooling should be done.
Based on the coolant used, the cooling methods can be classified into:
- Air cooling
- Oil cooling
- Oil and water cooling
Oil cooling is a commonly used method for cooling purposes.
The type of oil used in the transformer is mineral oil.
Characteristics of transformer oil:
- High dielectric breakdown
- Low viscosity
- Free from moisture
- Low pour point
- High flashpoint
Purpose of transformer oil
- Transfer of heat by convection, from winding and core to the cooling surfaces.
- It maintains the insulation of winding and extinguishes fire that occurs due to faults occurring in the windings.
Precaution in using Transformer oil:
- The insulating value of transformer oil is reduced due to the formation of sludge because of oxidation due to air and temperature.
- To minimize oxidation, the oil should not be exposed to air.
- Sludge is also formed due to the presence of acids and alkalis.
Drawbacks of sludge formation:
- Reduces the rate of heat transfer.
- Blocks the ducts.
- Increases the operating temperature
