What performance characteristics define mineral transformer oil for insulation and cooling?

Key characteristics include high breakdown voltage, low moisture content, low acidity, high resistivity, and low dissipation factor for strong insulation. For cooling, suitable viscosity and good thermal conductivity support circulation and heat transfer. Oxidation stability and inhibitor performance determine how well the oil resists sludge formation over time. Interfacial tension indicates contamination by polar compounds. Low gassing tendency and control of corrosive sulfur reduce risk to paper insulation and copper conductors. These properties are monitored by routine oil testing.