In this paper, the shortcomings and limitations of the transient stability marginbased on the extended equal area criterion (EEAC) method were investigated, and the effective range and its criterion of the transient stability margin based on the EEAC method werepresented.

The number of the segments is determined by an area criterion, and the curves to be matched are represented by an included angle chain of the same length.

Based on the linearized equal area criterion and small signal analysis,the Principle and techniques of Energy Storage System(ESS) Damping Power System Oscillations are proposed in this paper.

The equal area criterion is applied in the detailed mechanism study and the conclusions are: the effect of generator reactive power output increase on system angle stability is changing along with the fault cutting time.

By changing the fault point position, influence of three-phase reclosing sequence on system power angle stability is elaborated in theory according to the equal area criterion, based on which,the three-phase reclosing sequence of "the side with less reactance first" is proposed to enhance system power angle stability.

Based on the extended equal area criterion (EEAC), the proposed method can calculate the stability margin and dyn.

Concerned with a three phase to ground permanent fault occurred at the Anshun Switch Yard side on the 500 kV An-Tian transmission line in the South China power grid, the instability mechanism of the South China power grid when such a fault occurred is analyzed with the EEAC theory.

Based on extended equal area criterion (EEAC), an algorithm for assessing stability margin of generator-swing trajectories acquired by phasor measurement units (PMU) is presented.