A Novel Topological Approach to Examine Network Observability under a Contingency

A reliable state estimator to withstand a contingency becomes more and more important due to the increasing concerns on the network security in a deregulated power market. A novel topological approach is proposed in this paper to identify critical measurements and to examine network observability under a contingency, where the contingency can be any single branch outage or measurement loss. To advance the classical topological observability analysis, a new concept of contingency observability graph (COG) is introduced and it is proven that a power system network maintains its observability against a contingency if and only if its COG satisfies some conditions. With little extra computation load, the proposed COG based approach is a natural extension of the classical topological observability analysis for online applications. The IEEE 30-bus system is used to demonstrate the validity and efficiency of our approach.