Space weather events can cause geomagnetically induced currents (GICs) in power transmission networks. Over the past years, these currents have been measured in multiple substations in Austria, and the measurements have been tested against a model of local GIC with the aim of producing an optimized model, which can be developed through evaluation of various input parameters. We show the impact the choice of the local resistivity, in particular the surface conductivity in thin-sheet modeling, and the source of geomagnetic variations has on GIC modeling. In addition, the sensitivity of the model to the accuracy of the network configuration is also investigated. This encompasses the inclusion of power grids outside of Austria in the model as well as the consequences of removal of a substation either through transformer failure or active disconnection. Results show that a detailed surface conductivity model brings benefits to areas with large lateral conductivity variations and that there are certain substations that lead to increases and decreases of GIC in the rest of the network when removed. The importance of regionally representative geomagnetic field measurements is also highlighted and shown to impact model accuracy. This study concentrates on regional effects, but the results are also valid for large-scale studies elsewhere. node and adding four more stations in 2016 and 2017. The purpose of this paper is to expand on the former study using the same model and particularly to utilize measurements collected at multiple different stations to evaluate the importance and required accuracy of model input parameters for the best results.

Abstract. Geomagnetically induced currents (GICs) in power systems, which can lead to transformer damage over the short and the long term, are a result of space weather events and geomagnetic variations. For a long time, only high-latitude areas were considered to be at risk from these currents, but recent studies show that considerable GICs also appear in midlatitude and equatorial countries. In this paper, we present initial results from a GIC model using a thinsheet approach with detailed surface and subsurface conductivity models to compute the induced geoelectric field. The results are compared to measurements of direct currents in a transformer neutral and show very good agreement for shortperiod variations such as geomagnetic storms. Long-period signals such as quiet-day diurnal variations are not represented accurately, and we examine the cause of this misfit. The modelling of GICs from regionally varying geoelectric fields is discussed and shown to be an important factor contributing to overall model accuracy. We demonstrate that the Austrian power grid is susceptible to large GICs in the range of tens of amperes, particularly from strong geomagnetic variations in the east-west direction.

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