| The analysis and assessment of the transient stability of power system is one of the most fundamental and key issues in planning, operation and dispatchment of power system. With the continuous development of power system, more and more vast-interconnected power systems are operated nearby to the security and stability boundary in order to enhance economic efficiency. In the past few years in the world, there have been several large-scale cascading failures because of the unexpected trip of the protective relay. Therefore, it is very important to take into account of the operation features of protection during the analysis and assessment of transient stability, for this will make great sense in guaranteeing the safe and stable operation of power system.Based on ideas above, this thesis does some research on the assessment of the transient stability of power system with the protection operation. And the content and achievement of this thesis is as follows:Firstly, this thesis doses some research on the influence of the protection devices which have hidden failures to the stability of power system. The assessment of power system transient stability with the consideration of hidden failures is presented. The improved synthesizing index method is adopted to identify the critical line. Based on the study of the transient stability with the consideration of the protection devices, further analysis is focused on the impact of the critical protection which may have hidden failures; The critical energy of the power system is the minimal energy on the surface of the protection which is related to the critical line and its vulnerable area. The method based on the potential grad projected method is adopted to carry out the critical energy optimally.Secondly, based on the study of the protection elements and the protection, and applied them in the protection simulation, the complete model of the power system which can be applied in both simulation analysis and stability assessment is formed. Finally, the stability of the complete system with the consideration of the protection system is studied. The effect of the factor K of the timer is thoroughly analyzed. Trajectory sensitivity is adopted to compute the parameter's critical point of the timer for the specific fault and network. The accomplishments above accelerate the process of the transient stability analysis with the consideration of the protection, and lay a solid foundation for the further study. |
