Optimization of weighting factors of performance index to improve contingency ranking

Contingency screening and ranking are one of the most important issues for security assessment in the field of power system operation. The objective of contingency ranking is to quickly and accurately select the short list of critical contingencies from the large list of potential contingencies and rank them according to the severity. Contingency ranking is done on basis of calculation of Performance Index (PI), which measures the system deviation from the normal or steady state by identifying transmission line overloads as well as voltage limit violations at buses. In electric power systems, assignment of weighting factors to each bus and transmission line depends on the importance of specific bus and transmission line during power system operation. However, it is observed that while using weighted performance index, the weighting factor is assumed to be equal for all transmission lines, and generator outages, which leads to mis-ranking of potential contingencies. In this paper, an attempt is undertaken to adjust the appropriate and unequal weighting factors, in order to provide more accurate and realistic contingency ranking. Optimization of weighting factor is done using Quadratic Programming for IEEE 14 and 30 bus systems.