Transient stability prediction based on apparent impedance trajectory recorded by PMUs

Traditional methods for predicting transient stability of power systems such as the direct method, the time domain approach, and the energy function methods, do not work well for real-time stability predictions. The use of Phasor Measurement Units (PMUs) appears to alleviate this problem by providing information in real-time for transient stability assessment and enhancement. Techniques such as the rotor oscillation prediction method based on time series have made the prediction of system stability possible for real-time applications. However, such methods often require more than 300 ms after the start of a transient event to make reliable predictions. This paper proposes using the trajectory of the apparent impedance recorded by PMUs placed at strategic locations in the power system to rapidly predict transient stability. From the simulations performed, it is realized that system stability can be predicted in approximately 200 ms (12 cycles). The main advantage of this method is its simplicity as the PMUs can record the apparent impedance trajectories in real-time without any previous calculation. Moreover, using decision trees built in CART®, transient stability prediction becomes straightforward and computationally very fast. The optimum locations for PMU placement can also be determined using this technique.