Condition monitoring of transformer oil

A study of the factors affecting the ageing of mineral transformer oil has been undertaken at CSIRO Telecommunications and Industrial Physics in collaboration with TransGrid and Pacific Power. Oils from various manufacturers have been thermally and electrically aged in the laboratory and their ageing parameters have been compared with field samples taken from working transformers of the NSW electricity system. The standard ageing parameters such as acidity, interfacial tension, dielectric loss and moisture content have been measured together with the electrostatic charging tendency (ECT) which is being investigated as an additional diagnostic parameter. Instrumentation for measurement of ECT and tan /spl delta/ of flowing oil, has been developed. Results for laboratory and field aged samples are presented. Some implications for online condition monitoring are discussed.