Comprehensive approach of power system contingency analysis

Security of supply in power system supposes that the robustness of the system can be guaranteed in case of credible contingencies. This robustness relies on structural redundancy and on security margins. Traditionally, the "N-1" contingency analysis has been used for such check. This methodology leads to the definition of "sizing incidents", or credible contingencies. The system is said "N-1" secure if it remains within its operating domain for these "sizing incidents". Today some trends exist for relaxing the application of this criterion. This means that some emergency control actions must be implemented in the system for guaranteeing its security. This asks for their representation in the methodological approach used for evaluating the security of supply. This is not possible with traditional tools.