Transient Stability Monitoring for Electric Power Systems Using a Partial Energy Function

Practical methods are finally emerging for analyzing transient instability in electric power systems. Two approaches are evolving, one using global energy functions, and the other using partial energy functions. The global functions descend from Lyapunov theory and have a strong theoretical foundation. Partial Energy Functions are terms in the global energy function that correspond to a single machine. These Partial Energy Function (PEF) is heuristically defined and thus does not yet have a strong theoretical basis. This paper will focus on the PEF, its derivation, and its application. Much of the paper is in tutorial form. The paper first presents a clear and simple example to clarify the energy function approach. Then, a PEF is derived for a power system. The technique is applied to a 17 generator, 162 bus system. Stability margins are reported in megawatts.