An analysis of Australian power transformer failure modes, and comparison with international Surveys

Power transformers are expensive items, and a utility must decide when it is economically preferable to replace one, or when to invest in refurbishments or repairs. The expected probability of failure of a transformer is often used in this determination. A challenge frequently encountered by a utility when analyzing their power transformer data is that because this failure rate is so low, a population size larger than they own is required to make meaningful statistical conclusions. For the Australian region such extensive surveys are uncommon. International surveys have been produced on mode and probability of failure, but it is unknown how representative the data is for Australian usage. Consequently, a study was performed where the Australian utilities were surveyed to find the number of failures and retirements, and the age, when this occurred. Data on 630 failures and retirements was collected and then analysed. Proportions of failure modes are presented and discussed in this article.