What tests are included in electrical transformer oil testing programs?

Programs typically include BDV, moisture (Karl Fischer), acidity or neutralization number, interfacial tension, dissipation factor or tan delta, resistivity, inhibitor content for inhibited oils, and particle count for cleanliness. For condition based maintenance, dissolved gas analysis is central, often paired with furan analysis for paper aging and sometimes corrosive sulfur screening. Visual checks such as color and sediment are supportive but not decisive. Results are trended over time and linked to loading and temperature data to trigger filtration, regeneration, or repairs.