Published: 16. 4. 2024

CEZ will spend over CZK 400 million on investments and repairs of the Dlouhé stráně pumped storage plant this year, almost four times more than last year. Even slightly higher investments are planned for next year. This is related to the gradual renewal of important parts of the turbomachinery, which are slowly reaching the end of their service life after almost 30 years of operation. The main goal is to ensure reliable operation of the power plant in the future, which is increasingly important for the Czech power industry – in addition to covering morning and evening energy peaks, Dlouhé stráně is now used much more frequently as an energy accumulator, which serves to ensure balance in the transmission system in connection with the growing production of electricity from renewable sources.

“We are aware of the importance of Dlouhé strání and regularly invest in improving the reliability of the plant’s operation and safety. This year and next year will see important upgrades to the equipment of both sets. However, the work will definitely not end here, after 2030 we will have to make further and even more significant investments,” explained Róbert Heczko, Director of ČEZ Hydroelectric Power Plants.

This year’s main investments are focused on the TG2 turbomachinery – for example, the plan is to replace the stator winding and to re-centre the entire turbomachinery, upgrade the control system hardware, modernise the excitation, repair the hydraulic motors and recoat the internal water feeders from the upper tank to the turbine. In addition, many smaller works are planned, such as repairing the bridges on the road leading to the upper reservoir, and the installation of a stationary crane at the lower reservoir will also be important to ensure greater safety.

“We will be repairing a large part of the unit, which means that we have to pull the stator and rotor into position, i.e. to specially reinforced places in the turbine cavern. The repair of the shaft will also be technically demanding and will be carried out on a lathe in Pilsen,” said Ludvík Štrobl, the head of the power plant. The shaft, which is split into two parts, one of which weighs 28 and the other almost 33 tonnes, will be transported to Plzeň by specially adapted tractors.

The work, which began in early April, will last until early January 2025 and will involve dozens of workers from several Czech companies. From 19. 8. to 20. 9. 2024, when the TG1 turbine unit will also be shut down, will require a complete shutdown of the plant.

The Dlouhé stráně Pumped Storage Power Plant, whose engine room and other technologies are deep underground, serves as a huge accumulator of electricity. It also has certifications for black start service, voltage regulation, but the increasing importance of the plant lies in stabilizing the grid, in which the share of renewable energy sources is growing. Therefore, CEZ Group is regularly engaged in the modernization of the power plant. Last year, for example, the company invested CZK 111 million in improving the safety and reliability of its operations, and CZK 60 million in 2022. In 2021, the utility raised the operating level of the upper reservoir by 70 centimetres, allowing it to produce about 6 per cent more electricity per generation cycle than before.

Hydro pumped storage power plant Dlouhé stráně has three “bests”:

• the largest reverse water turbine in Europe – 325 MW,
• the power plant with the largest gradient in the Czech Republic – 510.7 m
• and the largest installed capacity in the Czech Republic – 2 x 325 MW.

Source.