What are the technical considerations for what oil is in a transformer?

The technical considerations for what oil is in a transformer include dielectric strength, thermal conductivity, and viscosity. The oil must have high dielectric strength to prevent electrical breakdown, adequate thermal conductivity for effective heat dissipation, and appropriate viscosity to ensure proper circulation within the transformer. Additionally, the oil should be stable at operating temperatures, resistant to oxidation, and compliant with environmental regulations. Common choices include mineral oil and ester-based fluids for their performance characteristics.