What parameters are defined in transformers oil specification standards?

Standards define limits and test methods for breakdown voltage, moisture content, acidity or neutralization number, dielectric dissipation factor, resistivity, interfacial tension, viscosity, density, oxidation stability, sulfur corrosivity, inhibitor content if applicable, and flash and fire points. They also specify sampling, handling, and acceptance criteria for new oil and sometimes for in service oil. These parameters ensure oil can provide insulation and cooling safely, and they support consistent procurement, maintenance decisions, and trending across an asset fleet.