Distribution system reliability assessment using hierarchical Markov modeling

Distribution system reliability assessment is concerned with power availability and power quality at each customer's service entrance. This paper presents a new method, termed hierarchical Markov modeling (HMM), which can perform predictive distribution system reliability assessment. HMM is unique in that it decomposes the reliability model based on power system topology, integrated protection systems and individual protection devices. This structure, which easily accommodates the effects of backup protection, fault isolation and load restoration, is compared to simpler reliability models. HMM is then used to assess the reliability of an existing utility distribution system and to explore the reliability impact of several design improvement options.