For a Secure and Sustainable Energy Future

Over a stretch of 7.7 kilometers, the River Our functions as the natural lower reservoir, providing a usable volume of 7.4 million m³ of water. Depending on the operating mode, the water level fluctuates between 219 and 228 meters above sea level.

The Loumillen dam, named after a former bark mill, impounds the lower reservoir at Vianden. Standing 30 meters high and 130 meters long, it also houses turbines that supply the power plant’s internal electricity network.

The upper reservoir is an artificially constructed lake with a perimeter of 5 kilometers. Like the lower reservoir, it provides a usable volume of 7.4 million m³, with its water level varying between 494 and 511 meters above sea level.

Four intakes connect the upper reservoir to the machines via pressure shafts. Intake 1 feeds machines 1–4, Intake 2 feeds machines 5–9, Intake 3 supplies machine 10, and Intake 4 supplies machine 11.

The underground cavern measures 330 meters in length, 17 meters in width, and 30 meters in height. Machines 1–9, each 23 meters long, operate as ternary units and generate 100 MW in turbine mode.

Machine 10 is installed in a vertical shaft 50 meters deep and 22 meters in diameter. With a capacity of 200 MW, it ranked among the most powerful pump‑turbines in the world during the 1970s.

Machine 11 was added as part of the most recent expansion. A dedicated cavern was constructed to accommodate the new 200 MW pump‑turbine.

Each motor‑generator unit is connected to its own transformer. For machines 1–9, the transformers are in a separate gallery where voltage is stepped up from 13,800 V to 220,000 V.

Four steel‑armored pressure shafts link the intakes to the machines. They overcome a vertical drop of 280 meters and feature internal diameters of up to 6.5 meters.

The tailrace tunnels connect the machines to the discharge structures in the lower reservoir. At their junction with the outlet structure, the tunnels reach diameters of up to 10 meters.

Access tunnels connect the caverns to the outside, enabling the passage of personnel as well as heavy‑load transport required for installation and maintenance work.

The outdoor switchyard links the unit transformers to Amprion’s extra‑high‑voltage grid, forming part of the wider European interconnected system.

The monitoring and control of the entire plant are centralized in the control room, which is staffed around the clock to ensure continuous and reliable operation.