What type of oil is used in transformers for cooling?

The type of oil used in transformers for cooling is primarily mineral oil, specifically refined insulating oil, which is designed for excellent thermal conductivity, electrical insulation, and stability under high temperatures. Additionally, there are also biodegradable ester oils for environmentally friendly options. Oil type transformer safety is crucial, as it not only prevents overheating but also reduces fire risks, ensuring the longevity and reliability of the transformer equipment.