Study On Life-Cycle-Cost Model And Its Application For Electrical Distribution Networks Considering The Reliability

This thesis was supported in part by the National Natural Science Foundation of China ("Study on the optimal switching model and algorithm for electrical distribution networks (EDN) using immune-algorithm", No.50307015) and the key project in Chongqing electric power corporation ("Study on the Cost-Benefit Analysis Model for EDN Based on the life cycle cost (LCC) principle"). The models of reliability evaluation and LCC analysis for the EDN are presented in this paper.The EDN has a significant impact on the reliability performance of load points due to connecting directly with customers. The reliability evaluation of EDN is becoming a popular research field in the world. During the useful life of components in an EDN, the investment cost of a component is only occurred at the beginning of installation, whereas the maintenance cost and outage loss are occurred at the beginning of each year, which is usually several times of the investment cost. Power system planners and managers must determine the optimal candidate schemes based on the LCC of the equipment and system. The reliability performance of an EDN, which is related to the investment cost of the installed equipments, directly affects the outage cost of the load points. Energy loss is a comprehensive economic index for an EDN. Therefore, the reliability performance and energy loss must be considered in the LCC models.This paper presents an equivalent analytical reliability evaluation model considering the switch faults. The LCC model and cost calculation methods for the EDN are proposed based on the cost-benefit principle and LCC theory, and the main contents are as follows:â‘ An algorithm for evaluating the reliability of EDN considering the switch faults is proposed based on the construction features of EDN. The reliability indices of load points and system in an EDN are related to not only the faults of transmission lines and transformers, but also these resulted from the switch faults. Hence, it must consider the impact of the switch faults on the system reliability. The adjacency list (AL) method is introduced to form the sections of an EDN. The impact of the switch faults on the system reliability is assigned to the adjacent sections based on the connection structure between the switches and the sections. An equivalent analytical model of reliability evaluation considering the switch faults is proposed. The calculation of reliability effect due to the switch faults can be performed without enumerating the faults of switches, and the calculation complexity of reliability evaluation for an EDN is reduced sharply. Results of the cases, i.e. the RBTS-bus6 and the RBTS-bus4 EDN, show that the proposed algorithm has an obvious advantage in saving calculation time and the engineering practicability.â‘¡The Life Cycle Cost (LCC) principle has been widely utilized to make good social and economic benefits in many fields. Cost calculation model of each part in LCC analysis is presented using the LCC theory and the cost-benefit analysis approach considering the investment time and discount rate. The calculation models for the investment cost, maintenance cost, outage loss, energy loss, etc are proposed. The LCC model considering the reliability effects of the switch faults and energy loss for the EDN is presented using the equivalent annual value method.â‘¢Power system load levels usually continue to grow with the economic development. The LCC model considering the load levels is proposed assuming that the load of transmission components, such as lines and transformers, always returns to the level of the previous planning cycle. The expected energy not supplied and the energy loss in one planning cycle are used to express the cost in life cycle. Application of the feeder 4 in the RBTS-bus6 shows that the proposed LCC model can be used to optimize the project schemes and improve the investment efficiency, and it is correct and practical.â‘£The algorithm for evaluating the reliability of EDN and the LCC model proposed in this paper was applied to a practical engineering EDN, i.e. the scheme optimization of 10kV Yuanzhong feeder in Shapingba District, Chongqing. The main purpose of this project is to improve the energy quality of the 10kV Jinliang feeder and the 10kV Gehuang feeder, such as the reliability and energy loss. Two schemes are proposed. The optimal is proposed based on the LCC analysis, sensitivity analysis of the economy and reliability for different schemes.