The equal area criterion is a graphical stability analysis method for large-disturbance (transient) rotor angle stability of a single synchronous machine connected to an infinite bus, derived from the nonlinear swing equation by showing that a stable post-disturbance trajectory requires the accelerating-power area and decelerating-power area on the power-angle curve, taken between the initial and final rotor angles, to be equal. This principle formalizes the distinction between small-signal (linearized) stability analysis, valid only for small disturbances, and large-signal stability analysis, which must retain the nonlinear power-angle relationship (P = Pmax·sinδ) because rotor angle excursions are too large to linearize; it belongs to power system dynamics and stability analysis within electrical power engineering.
The equal area criterion is a graphical stability analysis method for large-disturbance (transient) rotor angle stability of a single synchronous machine connected to an infinite bus, derived from th…