Why Transformer Oil Testing Is so Important?


Here we are discussing why transformer oil is very essential in our day to day life activities. Transformer oil or insulating oil is oil that maintains stable at high temperature and has great specialized electrical insulating properties. It is widely used in oil filled transformers.
Transformers are widely used by the electrical corporation. They transmit electrical power from one cycle to another. The oil encompassing by the coils in transformer supply cooling, insulation and safeguard against crown and arc. It is generally obtained by fractional purification and successive treatment of crude petroleum. That is why it is also referred as insulating oil.

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Transformer Oil Usage in Demands

Transformer oil usage is expected to grow in near future. Some countries, especially China and India, are the biggest consumers of transformer oils because of a major expansion of electric network increasing the establishment and up gradation of transformers, in turn, doubling the demands of transformer oil.  A minute transformer is distribution transformers, these are the biggest consumers of transformer oil.
After some years this oil is revealed to mechanical and electrical stress as well as chemical impurities. When the performance is diminished it can result in power disruption. To manage and extend transformer life and to avoid harsh breakdowns, regular testing of the transformer oil is very much essential.

Transformer Oil Testing

To evaluate the quality of the transformer oil testing, three steps are important to be carried out.

  • Dielectric  breakdown voltage
  • Moisture content
  • Power factor

Dielectric breakdown voltage

The dielectric breakdown voltage is a calculation of electric force that the transformer oil can confront without collapse. It is calculated by applying a voltage between two electrodes under prescribed quality under the oil. The dielectric test fixes the voltage at which the oil crack, which is symbolic of a number of impurities in the oil.
For mineral oil, a commonly accepted minimal dielectric strength is 30 KV for transformers with a high-voltage rating of 230 KV and above it another 27 KV for a transformer with a high-voltage rating below 230 KV. New oil should have a minimum dielectric strength of 35 KV by ATSM method of testing.

Moisture content

Moisture in oil is calculated in parts per million using the weight of moisture divided by the weight of oil. Water can be present in oil in a mixed form, as tiny droplets mixed with the oil, or in the Free State at the bottom of the tank holding the oil. Demulsification occurs when the tiny droplets merge with other minute droplets to form the larger drops which drop down to touch bottom and from free water. When the moisture in oil exceeds the saturation value, there will also be free water predicated from the oil in suspension or drops.
Generally, the moisture content in oil lessens the insulating structure, dielectric strength and allows flashover that can make a transformer collapse.
Power factor
Lets us tells you what we mean by the power factor of transformer oil? The power factor of transformer oil is equivalent to the cosine of the phase angle between an AC voltage applied and the resulting current. Power factor indicates the dielectric loss of the insulating oil and thus, it is dielectric heating. The power factor test is widely used as an acceptance and protective maintenance test for insulating oil.  A high power factor in service-aged oil identifies degradation, impurities, or both with moisture, carbon, or worsening products.

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