A serious failure of a large power transformer can
generate substantial costs for the transport to factory, repair and
financial losses resulting from power interruption. Therefore,
utilities have a clear incentive to assess the actual condition of high
voltage transformers, with the aim to minimize the risk of failures
and avoid forced unexpected outages. Special attention in this
respect is given to large transformers. In this paper, a general
FMECA for outage causes of 220 kV power transformers is
presented, including the local and final effects, and recommended
actions to avoid these outages. Assignment of risk priority
numbers to the various outage causes, which might occur at this
voltage level, are carefully considered.