What Are The Different Types Of Oils Used In Transformers?

What Type Of Oil Used In Transformers - ABC Transformers

The established names of distribution transformer manufacturers in India recommend paraffin based oil for oil-filled transformers. There are obvious reasons to prefer paraffin based oil over naphtha based oil in this South Asian subcontinent. Firstly, the warm climate of this region does not let the pour point of the transformer oil to be an important account. And secondly, the easy to get paraffin based oil makes it a preferable choice making it cost-efficient. The terminology of ‘pour point’ may have made you ponder and considering your doubt about the term, we will consider all the factors which can make the choice between the transformer oils. But before moving further, you should know that there are two types of transformer oil, viz. paraffin based transformer oil and naphtha based transformer oil.

Pour Point

Pour Point of transformer oil mostly relies on wax content in the oil. An experienced personal heading a renowned power distribution transformer explains pour point to be the measure of the base temperature at which oil begins to heat up under the standard test condition. In warm climatic areas, pour point of the transformer oil is not quite a considerable property. Instead, pour point of transformer oil is important to be acknowledged in those surrounding where the atmosphere is cold. It is because, in a cold climate, the oil is more susceptible to fall underneath the pour point. In this condition, the fallen temperature interferes with the transformer cooling system. When compared, paraffin based oil has a higher estimation of pour point than naphtha based oil. The latter measures of lower pour point because of its higher wax content.


The location for the setup of the transformer is considered for oil based transformers. This case is not common to the setup of the dry type distribution transformers because they do not have to be estimated with the pour point levels of the transformer oil. In the oil-based transformers, the type of transformer oil plays an important. It is specifically followed in the colder regions where the pour point of the transformer oil can become an issue which is why naphtha based oil is preferred in areas with a cold climate.

Oxidation rate

As per an expert dealing with the schneider distribution transformer, even though the oxidation rate of naphtha based oil is more than paraffin based oil, the sludge formed by the former is comparatively more soluble than the sludge from the paraffin based oil. This point brings light on how factors can conflict and have to be looked on a comparable scheme to which factor is more important for choosing the oil for the transformer.

Transformer cooling system

If the transformer oil is deteriorating the transformer cooling system, it becomes a matter of question to rethink on its usage. The preference of naphtha based oil over paraffin based oil rests on this matter only. The sludge from the naphtha based oil does not settle at the bottom which keeps the transformer cooling system free from any interference.


The easy access and availability of the transformer oil plays a considerable role majorly because it impacts the cost-effectiveness of the oil-based transformers. A clear example is India as we discussed above. When the smooth and reasonably available transformer oil is being considered, the business plan of oil cooled distribution transformer may not work on the best lines because the cost-effectiveness of the transformer oil can play quite an important role.

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