Reliability Assessment Of A Medium Voltage Distribution Networks And Parametric Analysis In Taiyuan

With the constantly advancing of electric power marketing, The user has not only confined to the power supply to be met, but also puts forward the new demand for power quality. By 2013, urban and rural power supply reliability reach 99.956%in the state power grid operation area, of which rural is 99.852%. Power supply reliability improve greatly, but there still exist some problem, such as mutual supply ability is poor,supply area is too broad, line insulation rates are low, layout is unreasonable and coordination problems in urban planning. Taiyuan’s distribution network power supply reliability is below the average level, the main reason lies in the city network structure is weak, the management of city network is extensive and distribution network automation level is not high. Therefore, it is imminent to promote the reliability research and improve power supply reliability of distribution. This article is base on it and evaluate Taiyuan’s distribution network reliability.This paper first introduces the forward-backward sweep method, the algorithm is validated by the IEEE 33 nodes network. On the basis of elaborating the related concepts of power distribution system, the several major research contents of reliability was introduced in detail, including:the reliability index of the system and load point, the assumption of reliability model, the model and calculation formula, which lay a foundation for reliability evaluation later.Based on the thorough analysis of complex medium-voltage distribution network, which is composed of multiple branch feeder, this paper proposes reliability evaluation method based on fault-spreading of multistage sub network.After analyzing of the reliability-network-equivalent algorithm and the failure diffusion, in the paper, distribution networks are divided into several multilevel sub-networks, which is base on the division point of circuit breakers and section switches. Then using the equivalent method to calculate the equivalent reliability parameters of each network, the load point and system reliability indices are obtained by failure pervasion of each sub-network fault. The contribution of circuit breakers, fuse and sections switches, reserve supply on the reliability indices, is taken into account. This algorithm has little computational burden and higher precision, which can be used for reliability calculation of any complex distribution system.The presented model and algorithm for reliability evaluation have been programmed to evaluate the reliability of the medium voltage distribution system in Taiyuan. The calculating output had good precision, which showed the effectiveness of the algorithms. The weak link has been discussed based on the sensitivity analysis of reliability parameters and four typical wiring patterns.This paper proposed to enhance the reliability by decreasing element error rate, decreasing maintenance time, making automation for distribution and gives the specific technical measures.