A Power system is said to be operating in a secure state if the system remains in a reliable, normal operating state for every contingency case under consideration. Due to time limitation in real-time situation those contingency cases which are potentially harmful to the system must be picked out and detailed analysis is to be carried out only for these cases. This process of ranking the contingencies according to their severities is referred to as contingency ranking.

In the proposed approach, the post contingent quantities are first expressed in fuzzy set notation. Then the heuristic rules employed by the system operators in contingency ranking are compiled and coded in the form of fuzzy reasoning rules. These reasoning rules form the basis for combining the evidence from each post contingent quantity and reaching the overall system severity index. In the fuzzy logic approach, voltage stability indices at the load buses are used in addition to the real power loadings and load bus voltage violations as the post-contingent quantities to evaluate the network contingency ranking. Simulation Results on IEEE - 14, 30, 39, 57 and 118 bus systems are presented.