SUPERIORITY OF CONTINGENCY RANKING METHOD USING CAPTURE RATIO IN POWER SYSTEM SECURITY ANALYSIS

Contingency analysis is best method to predict the power system condition, if any unwanted event like failure of single or multi transmission lines, generator outage etc., has occurred in the system. The process of identifying most critical contingency is determined with the help of contingency selection and this can be achieved by calculating performance indices such as power performance index (PIp) and Voltage performance index (PIv). Contingency selection method basically has two approaches, direct and indirect. In direct approach, the contingency ranking is done with the help of load flow program and in indirect approach, the contingency ranking is done with the help of some approximate method like distribution factor method etc. Ranking of most severe contingency can be determined on the basis of their performance index value. Prediction of best ranking method can be judged on the basis of their capture ratio and the CPU time or time taken in analysis. Here, in this paper, a new method based on Analytic Hierarchy Process (AHP) is proposed and analysis is carried out in detail for the impact of N-1 (single line outage) on interconnected power system. A new Capture ratio (NCr) is also proposed in this paper, which provides most promising results as compared to existing capture ratio calculation method. The effectiveness of the method has been tested on IEEE-118 bus test system. The proposed method is best suitable method of contingency ranking for implementation in online power system security checks.