Reliability analysis of 220 kV power transformers in Egypt

In this paper, outage data analysis of 220 kV power transformers is considered. Outagedata are obtained from the Egyptian Electricity Transmission Company. Outage-data analysis over 8 years from 2002 to 2009 of 252 transformers with MVA rating ranging from 40 MVA to 150 MVA is presented. Several indices are determined for evaluating the reliability of power transformers. The knowledge of these indices is essential for proper system planning and operation. Forced outages due to correct and false action of transformer’s protection systems are carefully considered. The trend of the determined hazard function indicated that a significant number of the transformers is probably being operated in the wear-out phase; however, detailed aging analysis is required to determine the reliability state of each transformer. The determined values for the maintainability and availability show significant variations with time. The results are compared with the IEEE 1979 survey.