Assessing the risk of geomagnetically induced currents in the German power grid

Abstract

Space weather driven geomagnetically induced currents (GICs) can disrupt the operation of electrically conducting systems like power grids and have thus received increased international interest. GICs occur under conditions of intense geomagnetic disturbance (GMD) as a result of the electric field induced in the conducting subsurface. Storm-time GMDs are particularly strong in the vicinity of the high-latitude ionospheric currents which are known to expand equatorward during extreme events putting mid-latitude regions at potential risk. However, a comprehensive GIC risk analysis for Germany has not been carried out so far. Here, we present current progress, challenges and future prospects towards this goal. We reduce the complexity of the problem by applying a 1-D conductivity model (EURISGIC) with a plane-wave approach in order to estimate the induced electric field from the GMD input (physical part) and constructing a preliminary model of the German high-voltage electricity transmission network from publicly available sources (engineering part). On the basis of this calculation chain we focus on the prevalent GMDs during strong past storm events in dependence of the associated space weather conditions (e.g., the auroral electrojet indices). Specifically, we investigate the horizontal GMDs as measured by geomagnetic observatories in Germany (including neighbors) with respect to both their magnitude and, if possible, spatial variability. We derive conclusions regarding the characteristics of the GMDs that pertain to elevated GIC risk levels in Germany as well as the controlling quantities, which should be included in a planned forecasting scheme.