What types of oil can be used in transformers?

Transformers typically use mineral oil, which is derived from refining crude oil, as the primary insulating and cooling medium. Additionally, synthetic esters, such as natural and synthetic ester fluids, are increasingly used due to their higher fire resistance and biodegradability. Silicone oils are also an option, offering excellent thermal stability. Each type of oil has specific properties that influence its suitability for different transformer applications and environmental considerations.