Reliability Study of a Selected Segment of a Medium-Voltage Distribution Network

Medium-voltage distribution networks are an important element of the global power system, being responsible for the distribution of electrical energy from transformer stations to local points of delivery and to transformer stations of lower voltage levels. The reliability of the operation of these networks has a direct impact on the continuity of energy supply and the level of unmet energy demand in the power system. The article presents a reliability analysis of a selected segment of a medium-voltage distribution network located in northern Poland. In this study, a probabilistic model of the operation process based on an eight-state graph describing successive levels of technical degradation of the analyzed network was applied. Transitions between the states of the model were described by failure intensities and restoration intensities of the system elements. On the basis of the Kolmogorov–Chapman state equations, the probabilities of the system being in particular operational states were determined. The results obtained were then used to assess the energy-related consequences of failures by linking state probabilities with the share of unmet energy demand. The analysis conducted enabled the identification of the most critical elements of the analyzed network structure and the determination of their impact on the energy supply capability of the distribution network. The obtained results may constitute a basis for planning operational activities, maintenance strategies, and modernization processes of medium-voltage distribution networks.