| Electrical distribution networks (EDNs) are connected directly with customers. It was researched that 80% of the total customer interruptions resulted from EDNs. So, at present, the electric power utilities are focusing on satisfying the demands of the customers and transmitting the electricity with high quality and reliability to the customers. This thesis makes systematic and thorough studies on the reliability evaluation models, the main factors impacting on reliability of EDNs, the primary measures to improve reliability and so on. The main contents are as follows.â‘ The basic concepts, reliability indices, classification, development and research work about the reliability evaluation of electric power systems are introduced in this thesis. Problems about reliability evaluation of EDNs are emphasized. Several EDNs' power flow calculation methods are compared, and a loadflow algorithm for radial distribution power networks is recommended since its simple expression, easy for programme and efficiency. Various reliability evaluation methods of EDNs are also compared and analyzed in this paper. The reliability evaluation algorithm for complex EDNs based on fault-spreading-method is introduced in detail, and its shortcoming that the exist of repetitive research and fault analysis is also pointed out.â‘¡ Aiming at overcoming the disadvantage of basic algorithm based on fault-spreading-method, this dissertation presents a novel method of reliability evaluation for EDNs, i.e., feeder- partition-algorithm. Based on the structure characteristics, the proposed method forms all minimum-isolated-zones of the EDNs using Width-First-Search technique. It applies the fault-spreading-method to determine the areas controlled by breaker and switching devices, and regards a minimum-isolated-zone not a component as a unit during the computing process of reliability evaluation. This method can save sharply time consumed in searching repeatedly the switching-devices. Assessment results of some RBTS systems and a 36-bus EDN show that the proposed algorithm has an obvious advantage in saving time and the engineering practicability.â‘¢ Based on the principle of Failure-Mode-and-Effect Analysis, the main factors impacting the reliability on EDNs are studied taking example for a simple EDN. The impact of saitching-devices deployment, automatic level of the system, the outage rate oflines and so on to the reliability of EDNs are analyzed in detail. According to the analysis, it is shown that the configuration of EDNs is one of the most important factors impacting reliability. Then the primary measures to improve the reliability of EDNs are summarized.(4) Applying the new algorithm and the conclusions above to the practical engineering EDNs, the excellent results have been acquired. A lOkV practical EDN in Guiyang City is evaluated by feeder- partition-algorithm, and the reliability indices of each node and feeder and the whole system are acquired. The relationship between the configuration of the EDN and its reliability is anatomized. At the same time, a scheme to improve the reliability of Doufu feeder is proposed aiming at its weakness.(D The economic performance of the improving scheme is also analyzed. The results show that the cost used to improve the reliability is far less than the benefit of reliability. The scheme shows the unification of reliability, economics and social benefit. Finally, the economic performance of improving reliability in the condition of different value per kWh and profit margin is compared.
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