Fuzzy Approach to Critical Bus Ranking Under Normal and Line Outage Contingencies

Identification of critical or weak buses for a given operating condition is an important task in theload dispatch centre. It has become more vital in view of the threat of voltage instability leading to voltagecollapse. This paper presents a Fuzzy approach for ranking critical buses in a power system under normaland network contingencies based on Line Flow index and voltage profiles at load buses. The line flow indexdetermines the maximum load that is possible to be connected to a bus in order to maintain stability beforethe system reaches its bifurcation point. Line flow index (LF index) along with voltage profiles at the loadbuses are represented in Fuzzy Set notation. Further they are evaluated using Fuzzy rules to computecriticality index. Based on this index, critical buses are ranked. The bus with highest rank is the weakest busas it can withstand a small amount of load before causing voltage collapse. The proposed method is testedon Five Bus Test System.