Research On Theory And Method Of Opening 500/220kV Electromagnetic Loop Network In High-voltage Power Grids

In order to meet the growing demand for electricity and transmit more high-quality power, power system need to build higher voltage network. The network structure can not be very strong early. It's a gradually improving and strengthening process. During the process, the lower and higher voltage networks often parallelly operate through the link of transformer's electromagnetic circuit. It's electromagnetic loop network. When local area loses high-voltage power, it transmits and accommodates power through low-voltage network. The loop network structure improves reliability and flexibility of power supply, but it brings about some adverse effects on operation management of power network. In recent years, the power-cutting accidents in large area happened frequently at home and abroad. They related to the electromagnetic loop network. Academia and engineering sectors agree that opening the loop network is an inevitable choice. Ultimately, the realization of power supply by delaminating and districting is orientation and aim of constructing large power grids. However, there is no uniform understanding of pivotal problems about opening the loop network, for example prerequisites and principias, estimation and choice of time and situs, hold and control of range and course etc.At present, with the gradual improvement of 500kV network structure, many 500/220kV electromagnetic loop networks in China have prerequisites of opening. In the course of opening, they are important problems that power system in China must solve at present, for example how to fully consider the impact of various factors, how to evaluate the multitudinous feasible schemes in order to institute felicitous opening course and scheme. In the thesis, the pivotal problems about opening the loop network are discussed, and a new integrative decision-making method based on rough sets theory and interval analytic hierarchy process is put forward. It includes:1. Starting from the basic concepts of electromagnetic loop network, its advantages and disadvantages are analysed theoretically. On this basis, traits of 500/220kV electromagnetic loop network in Guangxi, necessity and feasibility of opening are analysed. It lays the foundation of the research.2. Considering synthetically the main factors of opening electromagnetic loop network, focusing on its pivotal problems, its principias and process are concluded. Fulfiling the disconnection of 500/220kV electromagnetic loop network in Guangxi, its universality and operability are validated.3. In order to resolve the problem how to evaluate the multitudinous feasible schemes, a new integrative decision-making method based on rough sets theory and interval analytic hierarchy process is put forward. Its operability and validity are indicated by schemes decision-making of opening 500/220kV electromagnetic loop network in Guangxi.This thesis not only puts forward the implementary scheme of opening Guangxi's 500/220kV electromagnetic loop network in 2010, but also theoretically discusses the evaluation and decision-making method. The work carried out has a good engineering reference value and a theoretic significance.