How is FR3 oil for transformers tested for moisture and dielectric strength?

Moisture is typically measured by Karl Fischer titration in laboratories and can be screened with portable moisture analyzers in the field. Dielectric strength is measured with BDV test equipment using standardized electrode geometry and voltage rise rate. Because esters hold more moisture in solution than mineral oil, interpretation focuses on both moisture level and how it affects dielectric performance for the specific fluid. Testing is paired with acidity and dissipation factor trending to detect oxidation. Results are compared to acceptance criteria for new fluid and service limits for in use fluid.