Research On The Recognization Of The Critical Lines In Power Systems

In recent years, the frequent occurrence of blackouts in domestic and foreign countries brings new challenges to the research work of the security analysis of power system. In fact, most of these blackouts are caused by the cascading failures from an initial failure. In power system, there exist some important lines which play significant roles in the process of the cascading faults. If we can find out these lines and take certain measures to protect them, the probability of blackouts as well as cascading failures will descend. The major task of this paper is just to identify these critical lines according the structure and operating condition of the power grid. As there are numerous transmission lines in a practical power system, the conception and index of the edge-tenacity in network vulnerability assessment is firstly applied to power systems in this paper to reduce the computation burden. The mathematic model of screening out the critical lines is then built based on the topological structure of the power grids. In this model, edge tenacity is taken as the objective function and a set of edge cut is obtained by the discrete particle swarm optimization algorithm. So the screening of the lines is finished and the lines without significant influences to the major blackout are eliminated. After that, the index for the identification of key lines is advanced to identify the critical lines screened out in view of different operating conditions considering both the operational status of the system and the topological position. The IEEE30-bus system is used as an example to test and analysis the method in the paper. The application results have verified the effectiveness of the proposed model which could not only identify the key lines in different load level but also determined them statistically. The method proposed in this paper can provide some reference for the vulnerability assessment and maintenance of the power system.