Ranking of power system contingencies based on a risk quantification criterion

Contingency analysis is an integral part of modern energy management system. Traditionally, contingencies are analyzed to check a predefined, deterministic set of limit violations. Contingencies are then ranked according to the severity of the violations. However, this approach treats all contingency events equally likely; as far as the probability of occurrence is concerned. This paper describes a ranking approach that accounts for both the severity and likelihood of the underlying system contingencies. A risk-based contingency ranking (RCR) metric is developed which incorporates limit violations associated with bus voltages and transmission line thermal limits along with their failure rates. The proposed approach is applied to the IEEE 14 bus system and IEEE RTS 24 bus system. A comparison is carried out between the traditional contingency ranking based on severity only and the proposed approach using the RCR metric. The merits and limitations of each approach are further discussed in light of the current operating practices of power systems which include a growing number of uncertainties.