Geomagnetically induced currents (GICs), a result of solar wind interaction with the Earth's magnetic field and the resistive ground, are known to flow in power transmission grids, where they can lead to transformer damage and grid operation problems. In this study we present an analysis of five years of continuous GIC measurements in transformer neutral points in Austria. Seven self‐designed stand‐alone measurement systems are currently installed in the Austrian 220 and 380 kV transmission levels, measuring currents up to 25 A. We identify recurrent geomagnetic activity in the measurements, and also find man‐made sources of low frequency currents using frequency analysis. In order to support the transmission grid operators, two GIC simulation approaches are used to simulate GICs in the power grid. The first model uses measurements to derive the sensitivity of the location to northward and eastward geoelectric field components (which requires no detailed grid data), and the second model uses the detailed grid model to compute GICs from a geoelectric field. We evaluate two geomagnetic storms from September 2017 and May 2021 to discuss the effects of GICs on the power transmission grid and its assets.

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Solar storms impact electrical power grids by causing quasi‐DC neutral point currents in transformers. These currents lead to half‐cycle saturation as well as other related and unwanted effects in the grid. To reduce the effect of these currents on the grid, DC‐blocking devices can be installed or changes in the grid topology can be made. However, these counter measures often have unwanted side effects or cannot be applied to the grid due to operational restrictions. In this work, a novel mitigation approach, based on the distribution of currents on more transformers, is presented. The number and location of grounded transformer neutral points is optimized, taking grid related constraints such as the minimal number of transformer connections into account. It is shown that the algorithm can effectively reduce the stress on transformers without any additional assets and thus increase system security.

Solar storms impact electrical power grids by causing DC neutral point currents in transformers. These currents lead to half-cycle saturation as well as other related and unwanted effects in the grid. To reduce the effect of these currents on the grid, DC-blocking devices can be installed or changes in the grid topology can be made. However, these counter measures often have unwanted side effects or cannot be applied to the grid due to operational restrictions. In this work, a novel mitigation approach, based on the distribution of currents on more transformers, is presented. The number and location of grounded transformer neutral points is optimized, taking grid related constraints such as the minimal number of transformer connections into account. It is shown that the algorithm can effectively reduce the stress on transformers without any additional assets and thus increase system security.

<p>Geomagnetically induced currents (GICs) are a consequence of space weather activity that can affect power grid operation and stability worldwide. GICs manifest as quasi-direct currents flowing between the power grids and the conductive earth, and are often measured with a Hall sensor placed at the transformer neutral. Globally, the number of power grid substations with GIC measurements has grown quickly in recent years, but Austria remains one of the few countries with a dataset of long-term GIC observations. GIC measurements in substations in the Austrian power grid have been carried out since 2016, with a maximum of seven concurrent substation measurements, providing a unique opportunity for GIC measurement analysis.</p><p>In this study, we present an analysis of the last six years of GIC measurements in Austria. Seven custom-built stand-alone GIC measurement systems have been installed in the 220 and 380 kV transmission levels, measuring currents up to 25 A. We identify recurrent geomagnetic activity in the measurements, and also find man-made sources of low frequency currents using frequency analysis. We focus on two geomagnetic storms from September 2017 and May 2021 to discuss the effects of GICs on a mid-latitude power transmission grid. In conclusion, we find that there is a daily level of noise in the data and that, even during the largest events when 14 A were measured, transformer heating remains unlikely.</p>