Repair plans have now been finalised for the Limberg I and Limberg III pumped storage power plants after separate technical failures during testing and commissioning, Verbund has announced. The measures follow detailed damage analyses by the responsible suppliers, supported by external technical experts.
At Limberg III, investigations into the failure of both generator sets during commissioning trials have largely been completed. The analysis identified specific test scenarios in which exceptional mechanical loads acted on the rotors, leading to overstressing of the insulation system and subsequent failure. Given the project-specific design of the generators and the complexity of dismantling, the supplier ANDRITZ Hydro has decided to carry out repairs to both machines on site within the underground cavern. Based on the current schedule, commissioning of generator set 2 is expected to resume in summer 2026, followed by generator set 1 in winter 2026.
At Limberg I, a large transformer malfunctioned during black-start testing in early November 2025. The unit, which is under warranty, was inspected in the cavern by the manufacturer Royal Smit in the presence of VERBUND. The transformer is now being transported out of the plant for dismantling and detailed examination in a dedicated facility in the valley, with the aim of determining the precise cause of the failure. In parallel, arrangements for a replacement transformer have already been initiated, with a current delivery timeframe of around one year.
The outage at Limberg I removes 160MW of capacity, but this has limited system impact within VERBUND’s broader storage and pumped storage portfolio. Generation at Kaprun continues via Limberg II and the Kaprun main stage, allowing water from the large annual reservoirs to be utilised. Once Limberg III is commissioned, an additional 480MW of turbine capacity will be available, significantly increasing operational flexibility.
VERBUND estimates that the temporary loss of Limberg I and the delayed commissioning of Limberg III will result in a negative earnings impact of between €40 million and €60 million, largely concentrated in the 2026 financial year. The company currently operates around 25 storage and pumped storage power plants with approximately 4GW of turbine capacity and 2.4GW of pumping capacity, and continues to advance further pumped storage projects with a combined capacity of up to 2GW.
