Assessing insulators vulnerability to pollution-induced flashover for power system resilience studies

Environmental phenomena 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. Pollution represents a not negligible environmental cause of component outages, because it causes the flashover of insulators by different mechanisms. In order to increase the resilience of the power system against these events, a fundamental step consists of analyzing the vulnerabilities of insulators to pollutant deposits. The paper presents a model to quantify the vulnerability of insulators to two main mechanisms of flashover caused by deposits of pollutants under wet conditions and by snow accumulation in presence of sea salt. The model is integrated inside a resilience assessment tool and it can be used for different application contexts (from long term studies to operational planning support). The application of the tool to a realistic study case, referring to a portion of the Italian EHV/HV grid, demonstrates the effectiveness of the vulnerability model both in computing the return periods of outages of components due to pollution and in anticipating critical situations of power system.