Transformer design for high reliability

As the population of power transformers in service increases and becomes older, electric utilities are focusing attention on the availability of their plant. Users assess availability in terms of: (1) dependability-whether the transformer will be available in the short term, i.e. over the next 5 years; and (2) reliability-whether the transformer will be available in the longer term, i.e. over the next 5 to 15 years. Here, the author describes how it has become necessary for the transformer designer to accept that a transformer is a high integrity piece of equipment that is not expected to fail on test or in service. With this philosophy in place, the designer can be expected to provide designs that will give improved levels of reliability in service compared with previous generations of power transformers