Vulnerability of the Swiss electric power transmission grid against natural hazards

The synchronized European electric power transmission grid is one of the most complex networks and the Swiss transmission grid is central part of it. Natural phenomena, such as the occurrence of earthquakes or winter storms, may damage/destroy grid components and disrupt the normal operation of the electric-power infrastructure. A disruption may possibly propagate through the network and lead to problems in other areas, besides the geographical area directly affected by the natural phenomenon. This paper delineates the modelling of the earthquake and storm risk of a power transmission grid. The different model parts "hazard", "vulnerability" and "response" of the grid are explained with focus on the implemented statistical methods. The novel probabilistic winter storm model is explained in detail. The risks are estimated for the concrete case of the Swiss transmission grid, by using a large amount of Monte Carlo simulations. At the end, the risk from earthquakes and winter storms are compared. Outage of only a small number of grid elements was observed rather for winter storms than for earthquakes, while a large number of failed elements appear mostly for earthquakes. Although areas of Switzerland may lose the connectivity to the European transmission grid in large earthquake scenarios, the entire European transmission grid appears quite robust and stable.