An external system equivalent model using real-time measurements for system security evaluation

A model for an external system equivalent appropriate for real-time system security evaluation is proposed. The model has two components, one which models the reaction of the external system to system changes in past time intervals and a second component for adjusting the equivalent model to present operating levels. Decoupling techniques between P-δ and Q-V quantities at the boundaries are used in the model formulation and recursive system identification techniques are employed to obtain the parameters of the model. Numerical simulation studies made on the 1976 AEP-ECAR system show encouraging results. Possible further improvements and the need for testing with real time data are discussed and it is hoped that the paper will encourage others to devote effort to these and other pertinent issues.