Reliability and maintainability analysis of medium voltage transformers in Egypt

Abstract

Estimation of the reliability, availability, and maintainability (RAM) for power transformers provides the ability to predict their techno-economical performance and to assess the economic impact of their forced outages on power systems. In addition, RAM analysis can be used, for example, to enhance utility reliability planning, influence transformer design/technology, and improve maintenance/condition monitoring practices. In this paper, RAM analysis of power transformers in Egypt's power network is performed. The data are obtained from the Egyptian Electricity Transmission Company (EETC). The collected data are in the form of transformer outage reports for eight years, from 2002 to 2009, where the average number of transformers is 1922 in voltage populations ranging from 33 kV to 500 kV and MVA rating from 5 MVA to 500 MVA. Results show that true and estimated failure rates of power transformers in all voltage subpopulation are very high in comparison with the IEEE 1979 survey. In addition, the hazard functions show that the utility transformers in Egypt are operating in the wear out phase. It is also found that the availability and maintainability of the considered transformers are high in comparison with the IEEE 1979 survey.