Why are MIDEL oil filled transformers used in sensitive environments?

MIDEL fluids, typically ester based, provide high fire point and biodegradability, making them suitable for dense urban sites, indoor substations, tunnels, transport hubs, and environmentally sensitive locations near water. Using a less flammable fluid can reduce fire barrier requirements and improve overall safety case. Ester fluids also support insulation moisture management, which can benefit aging performance. Selection still requires validation of viscosity, cold start behavior, temperature rise, and utility acceptance for the specific transformer design and voltage class.