Abstract: One of the important aspects of modern power system security assessment is the consideration of any contingencies arises due to unplanned or planned line outages leading to system overloads or abnormal system voltages. Several methods have been developed in the past few years to address this problem but computation time has been identified as the constraint making the process inefficient. Utilities today are in need of tools, techniques and also the methods that will enable them to predict the dynamic stability and reliability of the grid in the real-time. A power system is secure against a given contingency if it operates within tolerable operating limits before and after the occurrence of the contingency. In practice, it is not possible to secure a power system against all possible contingencies. Therefore, only the most critical contingencies (imminent disturbances) are considered. Contingency ranking attempts to estimate the impact of various contingencies without actually solving the power network. Existing methods of contingency ranking methods suffer from masking effects in approximate methods and slow execution in more accurate ranking methods. This paper presents an exact and precise method of contingency ranking. The method used here takes due consideration of both apparent power overloading and voltage violations simultaneously to find indices which in turn used to rank the contingencies. Here 1P1Q solution is used to find the post contingency voltages and power flows. The proposed work is simulated on IEEE-14 and IEEE- 30 bus test systems in MATLAB environment. The method used is based on realistic approach taking practical situations into account. Besides taking real situations into consideration, this method is fast enough to be considered for on-line security analysis.
Keywords: Power system operation, power system security, contingency analysis, power system stability.