What are the specification types of transformer oil used in power transformers?

The specification types of transformer oil used in power transformers 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 specification type of transformer oil must meet standards such as ASTM D3487 or IEC 60296 to ensure performance and safety in electrical applications.