Model based resilience assessment and threats mitigation: a sensitivity based approach

Extreme weather events can determine large load disruptions on power systems; this calls for the analysis of the vulnerabilities to natural threats which may cause multiple, dependent contingencies. Given the high social and economic costs of such disruptions, the Transmission System Operators (TSOs) are interested in predicting these potential critical scenarios and in applying suitable preventive and/or corrective countermeasures to increase system resilience. The paper presents an in-depth resilience assessment methodology suitable, in operational planning mode, to predict the most risky contingencies which will affect the power system and, in the engineering mode, to analyse “what if” scenarios, by evaluating the system response under different assumptions for threat intensity and component vulnerability. The paper also provides a framework for operational and hardening countermeasures which can boost system resilience. In particular, the wet snow storm is the threat under study, and two mitigation measures are accounted for: the ice-phobic coatings of line conductors and the preventive redispatching of conventional generators to assure the minimum anti-icing currents. The sensitivity analyses carried out for different threat intensities on a model of the Italian EHV grid can help identify adequate mitigation measures.