Development of Short-Circuit Current Levels in Transmission Grids and Investigation of a Control-Based Reduction of the Short-Circuit Current Contributions from Power Units with Full-Size Converters

Abstract:
Developments in transmission grids, such as increasing meshing and the substitution of synchronous generators by power units with full-size converters, affect short-circuit (SC) current levels. Due to the limited SC current contributions of converters compared to synchronous generators, these changes initially suggest a reduction in SC current levels. However, the combination of increasing meshing and the fact that the increase in capacity of power units with full-size converters exceeds the reduction in capacity of synchronous generators can lead to higher SC currents. This paper investigates the effects of these developments on SC current levels using a generic transmission grid model with four expansion stages based on real transmission grid developments. The results show that increasing meshing significantly increase SC current levels. Some nodes show rising SC current levels despite a higher share of power units with full-size converters on the grid. To address potentially excessive SC currents, control-based measures to reduce the SC contributions of power units with full-size converters are investigated as an alternative to hardware-based measures. While effective in reducing SC currents, these measures may negatively impact grid stability. The findings highlight the need for individual strategies to manage SC currents while ensuring grid stability.