Grid-induced mechanical stress on the turbine-generator shaft

Seen from the turbine–generator shaft of a Nordic nuclear power plant, the changing power system is experienced as short, sometimes repeated torque disturbances. This report explains which grid events are most relevant for mechanical integrity, from faults and switching to classic sub-synchronous resonance and newer converter-driven interactions involving HVDC and inverter-based resources (IBR, including inverter-interfaced generation and loads). A key finding is that many risks remain difficult to confirm or rule out without adequate measurements. The report therefore focuses on practical actions that make risk visible and manageable: dedicated torsional or SSR protection, improved vibration monitoring and event recording, and routine post-event analysis linked to TSO data. These measures support faster investigations, better targeted maintenance, and more robust decisions as the Nordic grid continues to evolve.