Risk analysis of the electric power transmission grid

The subject of this paper is risk analysis of the electrical power transmission grid in Norway with focus on incidents that may lead to large or long-lasting loss of power supply. The main objective of the analysis has been to evaluate the robustness of the power transmission grid and to identify any weak areas in the main grid. The probability of two independent technical failures at the same time is negligible. However, in many cases the same incident may lead to failure of several components. This may be bad weather, cascade failures, terrorism etc. A storm may hit the grid at several places at once and the consequence may be loss of power delivery. How can these dependent failures be included in the analysis? In order to answer these complicated questions, a new and simplified method to evaluate the network vulnerability has been developed to analyse the Norwegian transmission grid. The method is illustrated by an example.