Analysis of AC transformer reliability

The reliability of the world's power transformer fleet has been reviewed. Of the more than 425,000 transformer years of operation collected, there were 1,204 major failures and 1,916 retirements from 66 utilities in 27 different countries. In addition to retirements and major failures, the age distribution was also analysed. As a result of increased emphasis on improving reliability over the life cycle, the failure rate has now fallen by more than half since the last Working Group. For all major failures, the hazard curve was fairly random with a slow increase with age.