An innovative methodology for risk-based resilience assessment to prioritize grid interventions against natural threats in the Italian power system

Abstract

In response to the increasing frequency of extreme natural events, Terna (the Italian TSO) and Ricerca sul Sistema Energetico—RSE, an Italian research centre in the energy sector, developed a risk-based methodology for assessing power system resilience. This methodology evaluates the benefits of grid hardening measures and supports Cost–Benefit Analyses (CBA) for resilience plans, as required by the Italian regulatory authority. A key innovation is the inclusion of climate change models to assess the evolving probability of natural threats, alongside traditional factors like supply security and renewable energy integration. The methodology primarily addresses wet snow and strong wind, which are major causes of grid disruptions in Italy, with plans to extend the framework to hydrogeological risks. The methodology uses analytical models based on international and national design standards to simulate grid component vulnerability. Unlike statistical approaches, this framework quantifies the effectiveness of countermeasures, such as adding anti-torsional devices to overhead lines. An advanced model is adopted to assess the vulnerability of lines to indirect effects of wet snow and wind, such as vegetation interference. By combining probabilistic models of extreme events with component vulnerability models, the methodology calculates failure return periods (RP) of grid components, subsequently substation outages and cascading failures are simulated. The key outputs are the return periods of substation outages and the Expected Energy Not Served (EENS) due to contingencies. A case study demonstrates the methodology’s effectiveness in prioritizing resilience interventions, showing good alignment between predicted failure RPs and actual fault data from the Italian transmission grid.

Bibliographic Information