Separation Criterion Based on Apparent Impedance Angle

In order to improve the criterion based on apparent impedance angle, the electrical parameters in the process of asynchronous oscillation based on the two-machine equivalent system are analyzed, and oscillation center is studied in the paper. In order to detect oscillation period correctly, the voltage and the active power is utilized. Moreover, the integration of reactive power is used to determine oscillation center. The simulation of New England 10 machine system shows that the criterion based on apparent impedance angle can distinguish asynchronous oscillation effectively, and oscillation period can be detected by voltage and active power. Also, the simulation indicates that oscillation center can be captured by reactive power.