By Iran Prado Arantes and Geraldo Nicola

A risk of a major equipment failure is one of the biggest worries of any transformer operator. A Brazilian electricity company presents a powerful example of how the improvements in the design standards for the transformer and reactor fleet lead to better safety, reliability and resilience of the entire substation in the long term.

Power transformers are highly reliable electrical equipment. Still, failures can occur regardless of the application of the best design, production and operation techniques. A global transformer reliability survey conducted by the Cigre working group A2.37 in 2015 concluded that the failure rate of substation transformers was 0.53% per year, and 0.95% per year for generator step-up transformers.

Such data leads us to estimate that a power transmission company can expect one or two failures per year for each group of 200 transformers in its fleet. This figure becomes more relevant when taking into perspective the potential impacts and external effects of each of these occurrences.

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This article was originally published in the December 2019 issue of the Critical Failure: Modes & Prevention magazine.

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