Evaluation of spare transformer requirements for distribution substations via chronological Monte Carlo simulation

This paper presents a new probabilistic methodology for sizing the number of spare transformers for a group of power distribution substations. Based on a chronological Monte Carlo simulation, the proposed methodology allows the assessment of several reliability indices and expected costs, even considering systems composed by transformers with different ages and non-exponential lifetimes. Real conditions of system operation, such as load transfers between transformers or substations, use of mobile units, and the replacement of failed transformers by spares, are duly modeled. In order to illustrate the proposed concepts, numerical examples using a real system are performed and the corresponding results properly discussed.