A direct numerical method for observability analysis

This paper presents an algebraic method that uses the triangular factors of singular, symmetric gain matrix to determine the observable islands of a measured power system. This is accomplished in a noniterative manner via the use of selected rows of tbe inverse factors. Implementation of the proposed method presents little additional effort, since sparse triangular factorization and forward/back substitution procedures common to existing state estimators, are the only required functions. The method is further extended for the choice of pseudo-measurements in order to merge the observable islands into a single observable system. Numerical examples are given to illustrate the details of the proposed methods.