Coherency recognition for transient stability studies using singular points

This paper describes a new method for the recognition of coherent machines for use in transient stability studies. The machine angles are compared for both the stable operating point, and for the unstable singular or equilibrium point corresponding to the system instability expected to result from the particular fault under study. The technique requires the solution of n-1 non-linear algebraic equations, where n is the number of machines. Results are described for a 25 machine system and the method is shown to have advantages compared with existing techniques.