Here you can find the position paper of the four transmission system operators on "Fault-Ride-Through" and on model requirements for electrolysis plants.
As the electrolysis plants are exposed to the voltage funnel and temporary voltage increases as a result of grid faults in the transmission grid, large quantities of electrolysis load could be disconnected from the grid in the event of a fault according to current connection rules. If several gigawatts of load were to disconnect from the grid suddenly and unplanned, this would not only have a massive impact on the power balance in the grid, but also on load flows and dynamic processes, which could jeopardize the stability of the grid with regard to the planned expansion of electrolysis plants. Voltage fluctuations (e.g. due to short circuits) cannot be completely ruled out at any grid node by the grid operator's existing technical measures. It is therefore necessary for system security that electrolysis plants can ride through these faults in the future (fault-ride-through).
The transmission system operators have formulated a consolidated position on this fundamental requirement for electrolysis plants, which will be needed in future to ensure system stability.