What parameters are measured during a transformer oil test according to IEC/ASTM standards?

Standard programs measure breakdown voltage, moisture content, acidity or neutralization number, dissipation factor, resistivity, and interfacial tension. Many utilities also include dissolved gas analysis, inhibitor content for inhibited oils, particle count for cleanliness, and corrosive sulfur screening depending on fleet risk. For insulation aging assessment, furan analysis is commonly used to estimate paper degradation. Standards define sampling, test temperatures, electrode geometry for BDV, and reporting formats so results can be trended reliably across time and compared against acceptance criteria.