What advantages does biodegradable transformer oil offer utilities?

Biodegradable transformer oils, typically natural ester fluids, reduce environmental impact in case of leaks because they break down faster than mineral oil. They also have higher fire point, improving fire safety and allowing use in sensitive locations such as urban substations, tunnels, and buildings. Many ester fluids tolerate higher moisture in oil while keeping paper drier due to moisture affinity, which can slow paper aging. Utilities also benefit from reduced remediation liability and improved sustainability metrics.