A risk-based resilience assessment tool to anticipate critical system conditions in case of natural threats

Natural events may affect the power system infrastructure, leading to multiple, dependent contingencies and widespread load disruptions. Given the high costs of these load disruptions, Transmission System Operators (TSOs) are interested in predicting potentially critical scenarios and in applying suitable preventive and/or corrective countermeasures. In order to increase the resilience of the power system against these events, a preliminary step consists of analyzing the vulnerabilities to natural threats. The paper presents a comprehensive methodology and tool for resilience assessment, based on an extended definition of risk and suitable to support operational planning (identifying the most risky contingencies) and to perform engineering studies on what-if scenarios. The selected contingencies are analyzed, by evaluating the system response under different assumptions on threat intensity and component vulnerability. The application of the tool to a realistic study case, referring to an emergency scenario in a portion of the Italian EHV/HV grid, show the added value of the proposed approach in predicting critical conditions in power system operation compared to conventional security analyses.