Transformer oil is a special type of oil that has excellent electrical insulating properties and is stable at high temperatures. It is used in oil-filled electrical power transformers to insulate, stop arcing and corona discharge, and to dissipate the heat of the transformer.

¹There are two main types of transformer oil used today: **paraffin-based** transformer oil and **naphtha-based** transformer oil. ²³⁴⁵⁶Paraffin-based oil is not as easily oxidized as naphtha-based oil, but the product of oxidation (sludge) is insoluble and precipitates at the bottom of the tank.

This sludge can obstruct the cooling system of the transformer and increase the risk of overheating. Paraffin-based oil also has a higher pour point than naphtha-based oil, which means it can become more viscous at low temperatures and affect the circulation of the oil.

However, paraffin-based oil is more widely available and cheaper than naphtha-based oil in some countries. ²³Naphtha-based oil is more easily oxidized than paraffin-based oil, but the product of oxidation (sludge) is more soluble and does not accumulate at the bottom of the tank.

This means it does not interfere with the cooling system of the transformer and maintains a better thermal conductivity. Naphtha-based oil also has a lower pour point than paraffin-based oil, which means it can flow more easily at low temperatures and ensure a better insulation. However, naphtha-based oil is less available and more expensive than paraffin-based oil in some countries.

²³There are also some other types of transformer oil that are not based on mineral oil, such as synthetic esters, natural esters, silicone oils, and fluorinated fluids. These types of transformer oil have different advantages and disadvantages depending on their engineering or environmental properties.

For example, synthetic esters have a higher fire point than mineral oils, which makes them safer for indoor applications. Natural esters are biodegradable and have a lower environmental impact than mineral oils. Silicone oils have a high dielectric strength and a low viscosity, but they are also more expensive and prone to leakage. Fluorinated fluids have a very high fire point and a very low viscosity, but they are also very costly and toxic. ¹I hope this answer was helpful for you.