An Augmented Facility Model for the Reliability Evaluation of Medium-Voltage Power Distribution Systems

Scheduled and failure outages of medium-voltage distribution facilities account for most of the interruptions experienced by customers, indicating the importance of accurate reliability evaluation of a medium-voltage distribution system. Traditional facility models do not differentiate constructing and maintenance outages. However, these two types of facility outages usually have different durations and need different optimisation strategies in practice. Therefore, traditional facility models limit the accuracy of reliability evaluation, especially in areas undergoing rapid development. This study proposes a 4-state medium-voltage distribution facility model and details the calculation algorithm of load-point and system reliability indices. The 4-state model regards constructing and maintenance outages as individual outage states and can reflect the effect of live-line working on outage rate. The model is verified using the topology of an existing feeder and actual outage data collected from the utility. Results show that reliability evaluation based on the 4-state medium-voltage distribution facility model is applicable to the analysis and planning practice of medium-voltage distribution systems. The results of reliability indices provide a quantitative basis for the formulation of optimisation strategies with a satisfactory accuracy.