A Method To Identify The Fault During Power Swing In The Power System And Detect The Fault Element Based On Wide Area Information

Along with the continual enlargement of power grid interconnection scale in China, the electrical contacts between interconnected local networks becomes closely,with the diversified operation mode of electricity market and the large number of operation of the advanced control techniques, the stability characteristics of power grid becomes complicated, the stability problem becomes more prominent. Among them, as an important means to guarantee the safety and stability of power system, reduce the risk of large-scale power failure, improve the power supply reliability and quality, the power swing block and the identifying technique of fault during power swing has to be studied in-depth.The emergence of wide area measurement system and the development of communication technology give new vitality to the relay protection. With multi point information of power system, wide area protection can cut fault fast, reliably and accurately, meanwhile wide area protection can analysis the effect on the safe and stable operation of the system of fault removal, it can take the corresponding control measures, improve the transmission line available capacity or reliability of system, and realize the function of relay protection and automatic control as well.A new method which can identify the occurring fault during the power swings and detect the fault's location based on area information in large power grids is proposed in this paper. Taking the influence that shifted frequency in power swings has on the algorithm for sequence current, this paper adopts a new concept integrated sequence current to make up the differential current, and it proposes a new theory called current differential protection to identify the occurring fault during the power swings in interconnected grids. With integrated sequence current in one end of the tie line as starting element, with integrated sequence current in double end of the tie line to make up current differential protection. This theory can improve the sensitivity in the fault with big transition resistance effectively and it can improve the problem of the low sensitivity in traditional negative sequence component in the fault near the center of the power swings.To identify the fault component in a further way, this paper designs an expression classification method of IED(intelligent electronic devices) and gives the corresponding expressions. This method uses the relationship matrix of intelligent electronic devices(IEDs) to describe the inter-relationship among the IEDs and relaying on the information of the direction of IEDs to decide which IED is connected to the fault component, it can find the fault component for which is the intersection of the protected objects of those IEDs, and it can locate the fault rapidly and accurately in power swings. Numerical examples show that the proposed wide-area protection is simple and easy to implement,it is immunity from the shifted frequency, the mode power system operates and it has strong resistance to the transition resistance, it can identify the occurring fault during the power swings and detect the fault's location well.