The equal-area criterion is a graphical/energy-based method for assessing transient (large-disturbance) rotor-angle stability of a synchronous machine connected to an infinite bus, based on the principle that a post-disturbance system returns to synchronous speed only if the accelerating-power area on the power-angle curve equals the available decelerating-power area before the rotor angle exceeds a maximum bounding angle. From this principle, the critical clearing angle and critical clearing time are derived as the maximum fault-clearing angle/time for which stability is preserved, computed via the swing equation and equal-area integrals for cases including a bus fault with zero power transfer, sudden loss of a parallel line, and a fault at or away from a line terminal. This belongs to power system analysis, specifically transient stability analysis, and extends the electromechanical swing-equation framework of rotor-angle dynamics to disturbance-clearing design criteria.
The equal-area criterion is a graphical/energy-based method for assessing transient (large-disturbance) rotor-angle stability of a synchronous machine connected to an infinite bus, based on the princ…