“[Interfacial Tension] covers the measurement, under non-equilibrium conditions, of the surface tension that an insulating liquid maintains against water. Interfacial tension is a measurement of the forces of attraction between molecules of the two liquids. It is expressed in milli-Newton per meter (mN/m). The test is an excellent means of detecting oil-soluble polar contaminants and oxidation products in mineral oils.”(Quote from IEEE C57.106-2015)
What method is used to analyze the sample?
How do you interpret the results?
What do the results indicate?
“Interfacial tension measurements on electrical insulating liquids provide a sensitive means of detecting small amounts of soluble polar contaminants and products of oxidation. A high value for new mineral insulating oil indicates the absence of most undesirable polar contaminants. The test is frequently applied to service-aged mineral oils as an indication of the degree of deterioration.” (Quote from ASTM D971-20)