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 m easured power system. This is accomplished in a noniterative manner via the use of selected rows of tbe inverse factors. Implementation of the propose d method presents little additional effort, since sparse triangular factori zation and forward/back substitution procedures common to existing state es timators, are the only required functions. The method is further extended f or the choice of pseudo-measurements in order to merge the observable islan ds into a single observable system. Numerical examples are given to illustr ate the details of the proposed methods.