Power plant in the heart of a rock is celebrating its 10th anniversary

The Dlouhe Strane pumped-storage hydro power station provides knight-services for the power system operation, says Zdenek Saturka responsible for CEZ Group´s hydro power plants management. It takes off energy from the system during the night whereas during the day it faciliates its supply. In case of need, it fills momentary outages operatively, he adds. The operation of the station is fully automated. The station can switch from stand to full turbine mode within 100 seconds, from stand to pump mode within 400 seconds and from pump to turbine operation within 150 seconds. If compared with a coal-fired unit start-up, it is a parameter appreciated especially by system operators controlling operation of the power system.

The plant, situated in the area of 95 hectares, is carefully integrated into the nature of the Jeseniky landscape protected area. Putting its technology under the ground was an evidence of the company´s commitment to the environment protection. The room it occupies inside the rock is considered as impressive throughout Europe. Both of its machine units are located in a 50 meters high cavern of 87.5 by 25.5 meters. The 6-tonne machines have a height of twenty four meters and their main parts are hiden under the turbine room floor; it is one of the highest underground caverns in Europe. It is necessary to go down eight floors to get as far as the bottom where are two Francis turbines. As well as the turbine cavern, there is a 115 meters long transformer chamber and other equipment underground. The underground system comprises 8,5 tunnels and drifts.

The plant uses a record head in the Czech Republic of 510.7 meters. During the periods with full output water runs through the turbine at the speed of 68.5 cubic maters per second, says Zdenek Saturka. The installed capacity of 650 MW is generated by two reverse turbine units. Switching from pump to turbine mode and vice versa enables to increase or decrease system load as much as by 1,300 MW, which is more than the capacity of one Temelin unit and nearly as much as the installed capacity of two large coal-fired plants of CEZ Group.

The public can be interested in the design of both reservoirs. The upper reservoir with the total volume of 2.72 cubic meters is located on the Dlouhe Strane mountain 1350 meter above the sea. To build the embankment of its dam it was necessary to extract 1.82 million cubic meters of material on the top of the mountain. The lower reservoir is located on the Divoka Desna stream, its capacity is 3.4 million cubic meters and the dam is 56 meters high. The upper reservoir is connected to the underground plant by two 1.5 kilometer penstocks; the lower reservoir is connected to the plant by two discharge tunnels with the diameter of over 5 meters. The dams of both reservoirs were built as rockfill dams and due to revegetation they have blended with the landscape.

A little hydro power plant equipped with a Francise turbine with the peak output of unit 0 of 163 MW, and using the energy of natural water outlet from the lower reservoir forms a part of the plant.

The pumped-storage hydro power plant Dlouhe Strane is admired not only by technicians, but also by the public. They can visit the information center in the site, which is the most frequently visited center of other similar CEZ Group´s offices, and which has a visit rate comparable to many historical landmarks in the Czech Republic.

Last year we were visited by 54,275 people, and this year´s development has indicated that the record could be surpassed. The plant has been visited by 350 people interested in top technics since the foundation of the center, says Miroslav Kopriva, current director of the plant development and a person who has dedicated a big part of his life to Dlouhe Strane. Today he is managing Energotis, an engineering company that, among others, operates an information center, too.

Due to the three superlatives, Dlouhe Strane has deservedly won an opinion poll conducted by iDNES news server and has been classified as one of the 7 wonders of the Czech Republic.

Ladislav Kriz
Press Officer, CEZ

---------------------------------

Dlouhe Strane fulfils several important functions in the power system static, dynamic and compensational. The static role of the plant is fulfilled through transformation of surplus energy in the system into peak energy at the time when thee is a surplus of energy in the system (mostly during the night), the water is pumped from the lower reservoir into the upper one, and in peak periods, when a shortage of energy occurs, the plant is switched to a turbine mode and it produces electricity. The dynamic function (dynamic functions, or ancillary services) of the pumped-storage power plant means that the plant functions as a backup output for the system, it can produce regulatory output and evergy and thus it contributes to the administration of the system frequency. The compensational mode of operation serves for regulating the voltage of the system. The power system must keep at disposal just as much electricity as needed at every moment, that is even at times when electricity consumption varies during the day and in longer periods as well.

The construction of the plant began in May 1978. But in the early 80s, the central bodies decided to hold up he project. In 1985, the design was modernized, and after 1989, it was decided to complete the project. The plant was modernized continuously also during the construction, so today it ranks among the most modern plants of its kind in Europe. Some important technological entities were imported Abel 400kV outlet from the French firm SILEC, enclosed 400 kV switch room from AEG Kassel, control system from AEG Wien, transfer circuit breakers from ABB Switzerland etc. The plant was put into operation in 1996.

Main participants of the development

Investor	CEZ, a. s., Vodni elektrarny Stechovice
Engineering investments supplier	Energotis, s. r. o., Loucna nad Desnou
General builder of the development	Ingstav, a. s., Opava
Technology general builder	CKD, a. s., Blansko
Underground works supplier	Subterra, a. s., TiĹˇnov
Supplier of penstock armouring	Hutni montaze, a. s., Ostrava
Supplier of transformers and motor generators	SKODA, a. s., Plzen
Supplier of control system installations	Montaze Cakovice, s. r. o.
Land property supplier	Pozemni stavby, Olomouc
Asphalt-concrete sealing supplier	Slovasfalt, a. s., Bratislava
General project engineer	Aquatis, a. s., Brno

4. 10. 2006