Reliability Assessment of Distribution Stations Considering Spare Transformer Sharing

A reliability study has been performed recently at Hydro One to evaluate the reliability of groups of distribution stations involved in a spare transformer sharing policy. The groups may include distribution utilities stations and distribution customer own stations. The study used a probabilistic method based on stationary Markov models and two performance criteria namely the group availability criterion and the total cost criterion in the evaluation. The study results demonstrate that the number of spare transformers required for the groups involved in the spare transformer sharing policy will be reduced while maintaining almost the same reliability levels of individual groups. The purpose of this paper is to describe the study, its reliability assessment method and to illustrate it using a sample system.