Reliability Assessment of Distribution Power Transformers Considering Load Transfer Capability

A number of reliability models based on stationary Markov processes were developed at Hydro One to evaluate the reliability of a group of similar distribution power transformers. Those models accounted for a number of factors that affected the reliability of the group. The factors included, in addition to the basic Markov model parameters, the redundancy and mobile unit transformer capability at each individual station. There was one factor namely the load transfer capability between the stations that was not considered in the reliability assessment. The objective of load transfer is to further reduce the impact of transformer outages on customers and therefore improve the overall reliability of the system. The policy of load transfer between distribution stations can be simple or complicated and that can have a significant impact on the overall system reliability. This paper describes a probabilistic method based on stationary Markov models for evaluating the impacts of load transfers on the reliability of distribution stations. An example of a real distribution system is used to illustrate the proposed method of assessment.