Generation Risk Assessment of Main Output Transformers
32nd Annual CNS Conference - 2011 June 05-08

Presented at:
32nd Annual CNS Conference
2011 June 05-08
Niagara Falls, Canada
Session Title:
PRA, Human Factors and Reliability

Mikko Jyrkama (University of Waterloo)
Mahesh Pandey (University of Waterloo)


The loss of large power transformers may have major implications for plant operation, performance, safety, and economics.  This paper examines the generation risk associated with main output transformers (MOTs) at a large nuclear station using the Monte Carlo simulation approach.  The developed methodology is used for spare inventory optimization and making transformer replacement projections, while taking into account the specific demographics and condition of the transformer population.  The transformer reliability is described using a flexible, three parameter mixed Expontial/Weibull lifetime distribution.  The results of the study indicate that, due to the long procurement time for large transformers, at least 1 or 2 spare transformers are needed immediately to minimize the risk to the station.  Delaying the investment, even for a single year, would increase the risk significantly.

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