Reliability Assessment For Power Distribution System Based On Bathtub-shaped Failure Rate Function

Power distribution system is mainly composed of transformers, distribution feeders, switches, buses and other electrical equipment. These devices are collectively referred to as components. The reliability evaluation of power distribution system is based on the reliability modeling of component. The accuracy and authenticity of component reliability modeling directly determines the accuracy and credibility of evaluation results. Most algorithms for distribution system reliability evaluation assume that the failure rate of component is constant, which can simplify the calculation process of reliability assessment, and the assessment results are mostly acceptable. However, the failure rates of components generally obey the bathtub curve, for the reason that components are affected by such factors as working conditions, maintenance level, internal aging and so on. So using the bathtub shaped failure rate function to calculate the reliability of distribution system is more universal and applicable.This paper summarized the related academic research about the bathtub shaped failure rate function, and selected the suitable distribution function to describe the distribution of component’s lifetime. The theory of probabilistic sequence was applied to calculate the probability distributions and the expectations of power distribution system reliability index, which overcame the defect of traditional analytical method that cannot deal with the non-exponential distribution system. In sequential Monte Carlo simulation, the non-homogeneous poisson process was applied to simulate the random fault process of components. The effectiveness of the proposed method was verified by a case study of RBTS-BUS6 system.