Research On Fast Operating Backup Protection System For Power System

The relay protection system is an important part of power network, and has a very close relation with the security and stabilization of the power network. Relay protection system relates to many aspects of power system, and should be considered with the systemic and global view, then it is possible for relay protection to play the function of "guarder of power network".The modern power system has put forward higher request for relay protection, and the large scale blackouts happened in U.S.A. and Europe in recent years have exposed the defects of backup protection. It is found that time setting following step principle for back-up protection can't meet the need of operating safely and steadily in power network, and strengthening the main protection or compressing the operating time of back-up protection can not settle the problem absolutely. Aiming at the problem, the thesis proposes the fast operating back-up protection(FBP) system, and researches on the key technology to realize FBP which can accelerate the operation speed of the back-up protection in the power network, optimize the integral performance of relay protection system, and improve the operation level of power network.The main contents of the thesis are as following:(1) The situations of back-up protection in power system are analyzed. Setting backup protection according to step principle will always lead to long fault clearing time of relays in backbone network as well as power plants, and further a threat against security of power network. Therefore, this thesis presents a new idea of fast operating backup protective relay system. Basic structure and operation principle of this FBP system in a substation are described, the hardware-software system of the FBP system is designed, and the functions of the FBP system are analyzed.(2) Through discussing the pickup unit of abrupt signals used commonly in the microprocessor-based protection, the thesis proposes the pickup unit of relay protection by the principle of wavelet analysis. By simulation, the results show that this method can enhance the sensibility and operating speed of pickup unit, improve the integral performance of the FBP system.(3) The directional relays based on fault components, traveling wave and energy function are discussed in detail, which are studied and used widely in the past 20years. On this basis, the thesis adopts the directional relay based on the sequence faultcomponents in the FBP system.(4) To the directional relay based on the sequence fault components, the extraction method of the sequence fault components accurately and quickly is studied, by analyzing the frequency responses of the algorithm of filtering sequence component. The thesis indicates that the algorithm of filtering sequence component has the ability of harmonic filtering, on this basis, the paper provides an idea to design the digital filter, and the algorithm of digital filter has been developed.