What are the types of oil used in power transformers?

The types of oil used in power transformers primarily include mineral oil, which is derived from refining crude oil, and synthetic esters, which are biodegradable and have higher fire safety ratings. Additionally, natural esters, derived from vegetable oils, are gaining popularity due to their environmental benefits. Each type of oil has specific properties that affect the thermal performance, insulation, and overall reliability of power transformers.