Testing, evaluation and standardisation of transformer oils

A number of activities within the IEC on the standardization on transformer insulating oils are discussed. Among these, it is of great importance the present recent (2003) of the standard IEC 60296 that introduces only one class of mineral oil to be employed in transformers with a reduced viscosity. The importance of sulphur compound level control in transformer oils is emphasized and more stringent sulphur level control tests are proposed; environmental concerns inherent with the use of mineral oils are also indicated. A proposal is made for an improved standard on partial discharge measurements on transformer insulating oils.