Influence of Inverter-Based Resources on the Planning of Short-Circuit Withstand and Breaking Capability in Transmission Grids

The continued integration of inverter-based resources (IBRs) leads to significant changes in short-circuit level (SCL) characteristics of several European control areas. The SCL is also affected by increased meshing due to additional transmission lines, substations, and the conversion of lines in the direction of multi-bundle conductors, which leads to decreased grid impedances. Today’s required equipment ratings, e.g. for busbars, breakers, or instrument transformers, are still mainly derived from short-circuit calculations per IEC 60909. However, highly simplified IBR models introduce substantial methodical uncertainty. This paper outlines three core challenges faced by transmission system planners: forecasting maximum shortcircuit levels, calculation-method accuracy, and identification of countermeasures. Overall, it becomes clear that the increasing demand for 80 kA-rated equipment across various European control areas presents a significant challenge due to the uncertain availability of components complying with the European F-gas regulation.