The Research And Application On The Reliability Of Rural Power Network Based On The Analysis Of Equipment Failure Rate And Distributed Generation Access

Traditionally, the research of distribution network reliability evaluation mainly focused on the urban electric network, the attention to the rural power grid level was relatively low. However, with the development of rural areas, especially the deepening of the new urban construction, the rural power supply reliability requirements of users is increasing, and the government regulatory agencies put forward higher requirements for rural power supply service. In January 2010, the Central Committee Document No.1 ―Opinions of the CPC Central Committee and State Council on increasing urban and rural development, consolidating the foundation of agriculture and rural development further‖ was released. It was proposed that to adapt to the rapid growth of rural electricity demand trend, a new round of rural power network upgrading project should be implemented and rural power network reliability and capacity should be upgraded. August 2015, the State Council adopted and published "Guiding Opinions on Accelerating the distribution grid construction and transformation" formulated by the National Development and Reform Commission. It clearly puts forward that the average annual outage time users in rural areas will be not more than 24 hours, the comprehensive voltage qualification rate will reach 97 % in 2020.In this paper, analysis and evaluation on several aspects of rural power network reliability is studied in detail. The main work and innovation includes the following aspects:1.The research history and present situation of rural power network reliability is reviewed in detail, including reliability evaluation algorithms of rural power network, reliability influence factors, basic data of rural power network reliability evaluation, as well as the facing challenges of rural power network reliability after the access of DG(distributed generation).2.To deal with the difficulties of acquisition of rural power network basic data for reliability analysis and poor management of rural power network when missing failure data, it is studied how to carry out reliability evaluation in spite of lack of fault data of the equipment, and a method for reliability evaluation of fault data missing element is proposed based on Weibull distribution. According to the characteristics of the actual operation of power system components database, the specific methods and processes for sample selection, parameter calculation, model checking, failure rate curve drawing and reliability evaluation of missing data elements is designed systematically. Transformers and log data of actual rural power network in Hebei is analyzed to verify the effectiveness of the proposed method. The results show that the voltage level, the manufacturer and the product model have great influence on the reliability of the transformer.3. A new element failure rate prediction model is proposed to deal with uncertainty and regional difference based on rural power network reliability prediction model. And reliability assessment for rural power grid is studied based on the model. The method is applied to develop element failure rate possibility and credibility distribution models on historical data of sample element. Moreover, a standard polyethylene sample element library is established according to fuzzy clustering analysis. An element failure rate prediction models according to credible distribution model and standard clustering failure rate interval value is established. And actual rural power network data is used to verify the proposed method. The result shows, by using this method, the final reliability evaluation result is closer to the actual statistics rural power network ability.4. A new fault recovery strategy is proposed based on network partition, considering the effects on rural power network reliability after the access of distributed generation(DG), and the approximate analytic expressions of random function for rural power network level and node level reliability index is derived. Through random sampling of random function expressions combined with non-parametric kernel density estimation algorithm, the probability density curve of reliability index of DG access is obtained. Using RBTS-BUS 6 reliability test system as example, the influence of distribution system reliability of different DG capacity configuration is analyzed. Comparing with the results of sequential Monte Carlo simulation, the correctness of the proposed model and the algorithm flow is verified. The influence of DG location and access capacity on the rural power network reliability probability distribution is analyzed based on the analytical calculation model.5.An example analysis based on the urban/rural power network of a city’s power supply reliability analysis data in 2014 is carried out, in which the quantitative comparison on the power network reliability between urban and rural area is presented and the further study on the optimization strategy to improve the supply reliability in rural area is carried out. A method that can distinguish the optimal sequencing of grid planning schemes is proposed, which proposes the basic principles and promotion Strategies for the grid reliability. Eventually, an example is given to illustrate the application and effectiveness of the method.6.A distribution network reliability automatic data acquisition and evaluation application is developed to solve the problems in reliability management, using the method in Chapter 2 and 3, and the model in Chapter 4. The design and development of rural power network reliability prediction system which is integrated into the power quality online monitoring platform as a subsystem is discussed. The validity and practicability of the system are verified by the analytical applications based on the actual data from 3 layers of surface: State Grid,provincial and municipal power network. From the result of online acquisition, calculation analysis and assessment scheme optimization, it can be seen that the system has good universality, and can be widely used in various forms of wiring in distribution network, and meets the reliability management of power supply units at all levels of distribution network.