Contingency ranking based on combination of severity indices in dynamic security analysis

This paper presents a novel severity index to analyze power system dynamic stability Application of severity indices in dynamic stability assessment is very complex and this paper proposes severity indices for dynamic contingency ranking These indices are based on the concept of coherency and three dot products of the system variables. Different coherency indices have been defined and then compared by ranking the contingencies according to these indices. It is well known that some indices work better than others for a particular power system. This paper along with
test results using several different systems  demonstrates that combination of indices provides better ranking than a single index. The presented
results are obtained through the use of power system simulation (PSS/E) and MATLAB 6.5 software