What advantages does FR3 oil provide for transformer fire safety and biodegradability?

FR3 is a natural ester fluid with higher fire point compared with mineral oil, which reduces the likelihood of sustained fire after an external fault or leak ignition. It is also readily biodegradable, lowering environmental impact if a spill occurs. FR3 can tolerate higher moisture in solution than mineral oil, which can help keep paper insulation drier by pulling moisture from paper into the fluid under equilibrium conditions. These advantages make it attractive for sensitive sites such as indoor installations, urban substations, and environmentally regulated areas.