The Research Of Limited Wide Area Intelligent Protection For High Voltage Grid

High voltage grid relay protection is indispensable as power grid security and stability first defending line, and the technology has been challenged by development of power system. Operation condition would be more complicated and security and stability problem would be more austere in large-scale interconnected power grid of high and ultra high voltage and transmission system of AC and DC technology. Flexible and multiplex operation mode is need in Smart Grid with character of distributed generation and microgrid. Traditional relay protection coordination would be destroyed in non-presupposed operation mode changed of structure power grid and catastrophe accidents of power grid. Generally, research of wide area protection based on wide area information is an effectual way to deal with the problem of power grid protection.The research of wide area protection principle and experiment system has been concerned widely, and necessary technology is provided with development of communication technology, intelligent measurement and control technology and digital substation, especially, Smart Grid should accelerate the application of wide area protection. Therefore, limited wide area protection system of centralized decision by area division was presented in this paper, combining with current wide area protection development and practical engineering application. And this paper gives a detail discuss on structure, principle and method of protected zone division, tripping strategy and intelligent protection principle.This paper brings forward a limited wide area intelligent protection system based on abundant power network information and intelligent technology by analyzing the practical application of wide area protection and further combining it with the recent development of power network. The system consists of some limited systems by covering with the wide area power grid, and forms the grid protection including integrated backup protection. The selection of protection is realized by exact fault judgment and power network structure, not for traditional multi section delay, so it avoids the accident of load transfer essentially.The principle and method of protected zone division has been researched by using graph theory. It is made up of not only information region, which is decided by wide area communication capability and expectant control range, but also selection of main substation which is decided by the degree of nodes in system. It is a feasible but not optimal way to deal with protected zone division for actual power grid, but it is fit for practical engineering and complicated loop power network.This paper makes some analysis and research on tripping strategy with connection mode in practical engineering, chooses tripping strategy by considering whole power grid not depending on action delay. Protection associated region is made use of identifying associated mode and selection of seed substation, which assures the backup protection duty for substations. At the same time, intelligent failure protection is provided with the function of breaker failure protection, and it is advancement for system intelligence.The basis and kernel of limited wide area intelligent protection system is fault identification, and it is very important to improve the identification veracity for engineering application. This paper gives an intelligent protection principle based on genetic algorithm, and it is a primary research for artificial intelligence application in protection. Conformation for regularization fitness function is good for intelligence principle standardization and expanding. Intelligence protection principle is made up of three expectation functions of main protection action information, fault direction information and impedance information, and the protection principle based on genetic algorithm has good accuracy and robustness, especially, excellent fault-tolerance capability by using logic relation of kinds of power grid information.In order to improve the capability of longitudinal direction comparison principle, this paper brings on a study of information fusion based on evolution model for assistant. This principle should be configured for the second protection principle of limited wide area intelligent protection, and it is useful to improve the capability of protection system, and this chapter also does some research on multiple criterion logic with two different protection principles. A communication system for wide area protection is mentioned in this chapter, and some simulation results for capability of communication system is educed by using Network Simulator. The simulation is about communication in different network environment and repetitious router transmitting, and compares communication delay and packet loss rate. The simulation results provide warrant for the selection of limited wide area radius.Finally the achieved research is concluded and future perspective on development of limited wide area intelligent protection is highlighted.