Practice of IEC 60422 in Ageing Assessment of In-service Transformers

Ageing assessment of transformer insulation is essential towards proposing asset management strategies. IEC 60422 is a standard that recommends not only a list of oil test parameters along with value ranges indicating good, fair and poor conditions; but also actions that can be employed. Nonetheless, the interpretation and implementation of IEC 60422 largely depend on utilities' own experience and expertise. Through analysing oil test databases of field transformers at 33 kV, 132 kV, 275 kV and 400 kV in the UK, the common parameters used for different utilities are found to be breakdown voltage, moisture, acidity and 2-furfural. Among them, acidity seems to be the most essential parameter in oil ageing assessment both from graphical analysis and statistical analysis in the form of…