What tests are performed on transformer oil samples?

Common tests include breakdown voltage, moisture content, acidity, interfacial tension, dissipation factor or tan delta, resistivity, inhibitor content, particle count, and color. DGA measures dissolved gases for fault diagnosis. Furan analysis indicates paper insulation aging. Some programs add corrosive sulfur tests, oxidation stability, and metal content screening. The exact test slate depends on asset criticality, oil type, and regulatory requirements. Results are trended over time to support condition assessment and maintenance decisions.