Czech Orlík hydroelectric power plant returns to full operation after spring repairs

Hydroelectric power plant Orlík is returning to full operation today after major spring repairs. It has a new control system, and two of its four units have been repaired. All four Orlík units can reach full output in under two minutes, and energy dispatchers use them mainly during the morning and afternoon peak demand periods, ČEZ spokesperson Martin Schreier told ČTK.

In March and April, energy workers carried out routine spring off-season maintenance in stages, this time on the third and fourth Orlík units. „Today we are returning unit TG3 to service. We have completed inspections of all the parts through which water flows during normal operation, including both 60-metre penstocks. The maintenance crews also worked on identifying defects, repairing cavitation damage by welding, and inspecting the 80-tonne turbine runners, which are 4.6 metres in diameter, for fatigue cracks,“ said Jaroslav Květ, head of operations at the Orlík hydroelectric power plant.

The Orlík power plant, remotely controlled from the central dispatch centre in Štěchovice, is the most important part of the Vltava cascade. In 128 seconds, it can supply the power system with 364 megawatts of balancing capacity. Regular investment in repairs is essential. „The recently completed replacement and migration of the control system, costing several million crowns, will enable us to guarantee that Orlík can provide balancing services to the modern energy system over the long term,“ said Róbert Heczko, director of ČEZ Hydroelectric Power Plants.

Maintenance is the only opportunity for specialists to enter the so-called waterways, where, during operation, up to 150 cubic metres of water per second flows through a single penstock at a speed of five metres per second. The water spins the turbine runner, whose energy is transferred by a shaft to the generator rotor. The electricity generated is fed into the Milín 220 kV substation. After leaving the power plant, the water continues downstream to generate electricity at Kamýk.

The Orlík hydroelectric power plant was commissioned in 1961–1962. Its most difficult hours—and the largest subsequent repairs in its history—came in the summer of 2002, when it withstood a thousand-year flood on the Vltava, at the cost of all four turbines and generators being flooded. The entire plant remained out of service for the following year, and the most severely damaged fourth unit did not resume supplying electricity to the grid until 13 December 2004.