Composite automated distribution system reliability model considering various automated substations

•We propose a set of composite reliability evaluation models.•We assess the role of automated substations on the distribution system reliability.•SAS plays a vital role in the enhancement of the distribution system reliability.•System reliability is significantly improved by implementing the DA schemes.•We rank various automated distribution systems based on their reliability. Due to the fact that automation can significantly improve reliability of substation as well as distribution system, this paper presents a composite reliability assessment model of distribution system which illustrates the impacts of substations automated by various automation configurations on the reliability of primary distribution systems equipped with a specific distribution automation (DA) scheme. First, three architectures of substation automation systems (SASs), known as ring, cascading, and star, are reviewed and their reliability block diagrams (RBDs) are developed. Reliability assessments for five types of automated substations are then done using the event tree and the concept of expectation methods. Afterwards, a particular automated distribution scheme designated as the low interruption system (LIS) is reviewed and the interaction between the SAS and the DA is then modeled using the event tree methodology. Finally, by presenting explicit formulas for reliability evaluations of the automated distribution system, the composite reliability assessment models are completed. The proposed approach is applied to the five distribution system configurations.