Which oil is used in transformers?

The oil commonly used in transformers is called transformer oil, or sometimes referred to as insulating oil. Transformer oil is a highly refined mineral oil that is specifically formulated to provide electrical insulation and heat dissipation in transformers. It is a type of mineral oil that has excellent dielectric properties, meaning it is a good electrical insulator, and it also has high thermal conductivity to help dissipate heat generated during transformer operation.

Transformer oil is typically a clear or slightly yellow liquid that is free from impurities and has a high flash point to ensure safety. It is used to insulate and cool the transformer's core and windings, preventing electrical breakdown and facilitating efficient operation. Additionally, transformer oil also helps to preserve the insulation materials within the transformer and protect them from moisture and oxidation.

While mineral oil is the most common type of transformer oil, other types such as silicone-based oils and synthetic ester-based oils are also used in certain specialized transformers or in environmentally sensitive applications. These alternative oils offer different advantages such as enhanced fire safety or biodegradability, depending on the specific requirements of the transformer and its operating environment.