Which oil is used in Transformer?
Three types of cooling oils or liquids are used in transformer tank today.
- Inflammable – Mineral oil
- Low flammable – Silicon liquids
- Non-flammable – Hydrocarbon liquid
Commonly in transformer mineral oil is used, which is obtained by refining crude petroleum. Clean and dry mineral oil is an excellent insulator. Its small loss by evaporation.
Great care should be taken to keep the oil away from flame and moisture because it is an inflammable liquid and readily absorbs moisture from the air.
Mineral transformer oil is replace by Synthetic liquids because it do not catch fire easily therefore those transformers used in
- Underground mines
- Refineries and hazardous location
- Workshop and plants of metal processing and cinemas etc.
Transformer oil consists of namely paraffin, naphthalene and aromatics organic compounds. All these are hydro carbons, hence transformer oil known as ASKARELS and PYROCLORE are also in use.
Properties of Transformer oil
A good transformer oil should have the following properties:
- High specific resistance so that high insulation resistance.
- Better heat conductivity, it means higher specific heat.
- High firing point, so that it does not catch fire at low temperature.
- When exposed to air, do not absorb moisture easily.
- Low viscosity.
Necessity of transformer oil
Large capacity distribution transformers has losses occur like core losses and copper losses on load due to which it produces more heat. It is necessary to reduce the heat within temperature class limit by providing suitable insulating materials.
Transformer oil acts as a good electrical insulating material and it reduces electrical break down. It will also act as cooling agent, thus it brings thermal stability to all the internal parts of transformer.
Causes for deterioration of oil
When the transformers are use on load, the oils of the transformers are normally deterioration due to following conditions of uses.
The oil may come in contact with the air, therefore moisture and dust added in the oil. Due to presence of moisture, it affects the electrical characteristics of oil and will increase the speed of deterioration of insulating oil.
Sediment and precipitable sludge may be formed on the winding and core surfaces, therefore it will reduce the cooling rate of the insulating materials.
The presence of certain dissolved metallic compounds will increase the acidity of oil. In such cases, the resistivity decreases, and electrical strength also decreases, and it is also the causes for deterioration of oil.
Download MCQ PDF of Module 13: Transformer.
- Transformer – Principle – Classification – EMF Equation.
- Transformer losses – OC and SC test – efficiency – Voltage Regulation.
- Parallel operation of two single phase transformers.
- Three Phase transformer – Connections.
- Cooling of transformer – testing.
- Small transformer winding – Winding machine.
- General maintenance of three-phase transformers.
MCQ Question PDF of Transformer