Study On The Optimization Of Voltage Grade Under Urban-rural Integration

The planning of power distribution network is a comprehensive problem involved with many aspects, such as power load characteristics and load forecasting, power flow calculation, power losses, reliability analysis, distribution automation and external factors such as economic development and policy changes and so on. Meanwhile, as the connection of transmission network and consumers facilities, it is so important that we have to do it well in order to get a high quality and low cost power supply system. Taking the urban and rural integration as a turning point, with "Study on the optimization of voltage grade under urban-rural integration" as its basic research object, this article analyzes the influence on the planning of power network while power supply environment changes, proposes a corresponding power network planning strategy with changed environment.The integration of urban and rural is an important way to solve the "Problems of PAC(Peasants, Agriculture and the Whole Countryside)" problem. Many provinces and areas have put the urban-rural integration into the development planning of next five years. The integration of urban and rural has become an inevitable trend in the development of our society. So this article takes the development of urban and rural integration as the change of power supply environment, through the introduce the development process of the urban and rural integration at home and abroad, expounds the essence of urban and rural integration and its main content, and then analyzes the layout characteristics of the urban and rural integration.As one of the basic steps in distribution network planning, rational scheming of voltage grades has been selected to research in this paper. Researching for optimum voltage grade sequence and rational scheming of medium voltage of distribution network has important practical significance. Basic on the analysis of significance of rational scheming of voltage grades and the present situation about voltage level scheming in some developed countries as well as in most areas in China, the optimization direction of voltage grades is put forward, and a multi-objective optimization model comprehensively considering the economical, technical and social factors is established. The economy index uses comprehensive annual fee including the investment, the cost of line losses and operation and maintenance cost. The optimization processes are as follows:choosing some rational schemes of voltage grade sequence for preliminary optimization, and then comparing the selected schemes with selected objective based on the global optimized network structure, and eventually getting the optimal scheme of voltage grades. The economically technical index is an important factor for choosing the best voltage grades for the power network. The calculation of the correlation network structure index is the key. An optimized network model aimed at the lowest comprehensive annual fee is built based on the statistic data. The best voltage grade sequence can be chosen according to the result with economical transformer's outlines and capacitance changing along with the load density, and so does the section of the lines. Therefore, the dynamic model is more reasonable, effective and feasible than use special indexes.Considering the influence of urban-rural integration layout on power network planning, using the established voltage grade optimization model, a voltage grade optimization method under urban-rural integration is put forward. Combining the layout characteristics of the urban-rural integration, voltage grade optimum target under urban-rural integration is determined, preliminary schemes of voltage grade sequence are selected, parameters are set, evaluation method is built and the optimum voltage grade scheme under the layout of urban-rural integration is obtained. The conclusions can not only be applied to evaluate the existing voltage grade scheme, but also can be used for directing the planning and construction of new power network in urban-rural integrated areas.