Limberg I and III: Repair plans for Kaprun are now available

The damage analyses of the two generators of the Limberg III pumped storage power plant that failed during commissioning tests have largely been completed by the supplier responsible and a repair plan for the generators has been put forward. To restore the Limberg I pumped storage power plant to working order, the process of organising the delivery of a new large-scale transformer began at the same time as the evaluation of the exact cause of the damage.

Limberg III: Generators will be repaired in power plant cavern  

Generators for large pumped storage facilities, such as those in Limberg III in Kaprun, are custom-made products tailored to each project. Testing during commissioning therefore plays a particularly important role. To ensure that these special generator sets operate under the specified loads, their suitability is tested in a precisely defined trial operation. For Limberg III, these tests showed that the rotors are exposed to particularly high forces in possible exceptional cases, which the manufacturer says led to excess strain on the insulation system and subsequently to failure.

As a result of the comprehensive damage analysis, which also involved an external expert, ANDRITZ Hydro has decided to carry out extensive repairs to both generator sets at the same time on site in the cavern to ensure stable continuous operation. 

The repair plan states that the interrupted commissioning of generator set 2 can be continued in summer 2026 and generator set 1 in winter 2026.

Limberg I: Replacement of faulty transformer 

The large-scale transformer, which malfunctioned during black start testing in Kaprun at the beginning of November 2025 and is under warranty, was inspected by the manufacturer Royal Smit in the power plant cavern in the presence of VERBUND. The decision was made to transport the defective transformer into the valley by the end of this week for a precise damage analysis. There, the transformer will be taken to a specially prepared hall under the supervision of VERBUND and external experts. The planned dismantling should help to determine the cause of the damage.

The process of organising the delivery of a new transformer has already begun in order to ensure that Limberg I is brought back into working order as quickly as possible. As things stand, VERBUND has been promised a delivery period of around one year.

Energy market impacts

Pumped storage power plants such as Limberg I and III are long-term projects that will be needed in the coming decades for a renewable and resilient energy future. Demand for electricity in Austria is rising due to decarbonisation and the aim to reduce dependency on imports. According to current forecasts, wind and PV capacities are expected to at least quadruple as a result of this.

Carbon-free storage and flexibility capacities are needed to ensure that the fluctuating feed-in of these technologies can be safely integrated into the grid. The expansion of pumped storage facilities, including Limberg III, is therefore key to maintaining the security of supply in the coming decades.

The total turbine capacity of VERBUND’s storage and pumped storage power plants (excluding Limberg III which is still in the commissioning phase) is currently approx. 4 GW turbine output and 2.4 GW pumping capacity. Of these, only 160 MW from Limberg I is currently not available. This outage has minimal impact on the overall situation in Austria and also does not affect production in Kaprun, because the water from the large annual storage facilities can still be processed with Limberg II and Kaprun-Hauptstufe. Once Limberg III is back on the grid, there will be 480 MW of additional capacity, which will increase flexibility.

According to current estimates, the negative impact on the Group’s result from the temporary loss of Limberg I and the delayed commissioning of Limberg III is expected to be between €40 million and €60 million. The vast majority of this relates to the 2026 financial year.

Storage and pumped storage power plants at VERBUND

VERBUND currently operates around 25 storage and pumped storage power plants with approx. 4 GW turbine capacity and 2.4 GW pump capacity (storage capacity 1,800 GWh)

• 17 storage power plants with 1.3 GW turbine capacity
• 8 pumped storage power plants: 2.7 GW turbine capacity, 2.4 GW pumping capacity
• In the past 15 years alone, VERBUND has invested around €1.2 billion in storage and pumped storage power plants in order to increase flexibility (approx. 1.1 GW turbine capacity and approx. 1.2 GW pump capacity).
• Other VERBUND pumped storage projects with a turbine and pump capacity of up to 2 GW are being implemented, approved and planned.