Why is silicone oil used in transformer fire-safe applications?

Silicone oil is used because it has high fire resistance, high flash and fire points, and good thermal stability. This reduces fire risk in high consequence locations such as buildings, tunnels, and urban substations where mineral oil fire hazards are unacceptable. Silicone fluids can also perform well across a wide temperature range. The tradeoff is higher cost and different handling and compatibility considerations. Utilities choose silicone oil when fire safety and risk reduction outweigh the premium price.