Real time transient instability detection based on trajectory characteristics and transient energy

Wide area protection based on phasor measurements have become more and more important research issue. A method is proposed for fast and accurate real time detection of transient instability based on the wide area measurements. Trajectory characteristic and transient energy are synthesized to improve the detection accuracy for complex power system. The relationship between trajectory characteristic and transient energy is deduced. Trajectory characteristic method is developed by utilization of curve fitting of angular velocity and reevaluation on dual-cluster identification. That avoids certain wrong identifications. The calculation of transient energy is introduced to analyze energy transformation, and a sub-criterion is presented. Simulations are carried out on the IEEE 39 bus system and China Southern Power Grid. The results indicate that the proposed method is effective and reliable in determining the loss of synchronism.