Online dynamic security assessment of power systems using critical group energy function

This paper presents a method for online dynamic security assessment using the energy function of a group of generators. Using the centre of inertia (COI) reference, the energy function of the individual generator is computed. This paper proposes the use of the energy function of a set of generators called the critical group instead of the total energy function. A procedure based on heuristics is used for the determination of the critical group and the critical clearing time is estimated using the energy function of the critical group. Case studies on 10 Generator New England System and 50 Generator IEEE Transient Stability Test System with realistic generator model are presented. In general, the values so obtained are found to be more accurate than those obtained using the total system energy function.