Service experience of large substation transformers in Australia

Substation transformers constitute a significant portion of the overall capital investment in a large transmission system. Stringent but realistic requirements on performance and testing need to be clearly understood and specified. To ensure reliable in-service performance, the technical requirements must be supplemented by adequate quality-assurance systems during design and manufacture, and an effective maintenance system during service. The author gives a broad overview of more than three decades of in-service experience with various types of substation transformers by the Electricity Commission of New South Wales, Australia. The author describes technical, testing and quality requirements and discusses aspects of transformer operation, in-service performance and failures. The author also examines some aspects of transformer maintenance, particularly diagnostic techniques for early fault detection in ageing transformers, and the impact of some technological developments on design and performance of HV and EHV power transformers