What steps are included in a standard transformer oil testing procedure?

A standard procedure starts with clean, representative sampling using a sealed valve and proper bottles, avoiding air and moisture pickup. Lab or field testing then typically includes BDV breakdown voltage, moisture (Karl Fischer), acidity, dielectric dissipation factor (tan delta or power factor), resistivity, and interfacial tension. DGA is added for fault detection, and furan testing for paper aging when needed. Results are compared against acceptance criteria and trended with prior samples to decide on filtration, dehydration, regeneration, or oil replacement.