When should silicone oil for transformers be used instead of mineral oil?

Use silicone oil when fire safety requirements are strict, such as indoor substations, high occupancy buildings, or locations where mineral oil fire risk is unacceptable. It is also selected where thermal stability and wide ambient temperature performance are important. Mineral oil remains preferred for cost and broad utility acceptance, so silicone is typically a risk driven decision. Before choosing, confirm transformer design compatibility, containment requirements, and maintenance practices, because silicone fluids can differ from mineral oils in handling and procurement.