Pumped storage power plant Dlouhe Strane (CZ)
Today we share really exciting experience with you – a visit of pumped storage hydro power plant Dlouhe Strane located in Jeseniky mountains in the Czech Republic. The power plant is operated by CEZ [1] and there is an info center for visitors. It is recommended to book the excursions in advance as the number of visitors is limited. You can choose between shorter tour (without trip to upper reservoir) and longer tour (incl. visit of upper reservoir).
The hydroelectric power plant is located in Northern Moravia in land register of Loucna nad Desnou. Purpose of pumped storage hydro power plants is explained in the introduction article [2]. Dlouhe Strane is positioned in a protected landscape area of Jeseniky mountains and the visit of upper reservoir offers a breathtaking view on the surrounding mountains. The area is popular tourist place in winter for skiing and appreciated by mountain bikers in the summer season.
The power plant itself is very popular as well. Several thousands of tourists visit the power plant each year. In 2019 the number of visitors exceeded 93’000 and the “industrial tourism” is booming.
The lower reservoir is supplied from Desna river. The upper reservoir is man-made by cutting the peak of Mravenecnik.
Records of Dlouhe Strane hydro power plant
Dlouhe Strane pumped hydro storage power plant holds three records:
– Biggest hydro power plant in the Czech Republic based on total installed power (2 x 325 MW)
– Hydro power plant with highest water head in the Czech Republic (in average 510.6 m)
– Largest reversible turbine in Europe (325 MW each turbine-generator set)
Few superlatives
– Every day approx. 2.6 million m3 of water used to be pumped (equals the volume of upper reservoir). Recently the volume increased as due to renewable sources the power plant operates several times per day.
– The area of upper reservoir is equivalent of 15 soccer playgrounds.
– In year 2005 the power plant was listed among 7 wonders of Czech Republic.
History of Dlouhe Strane
Construction of the hydroelectric power plant started in 1978 after a thorough selection of best location. The site construction was interrupted for a while, but later decided to be finished. Commissioning of the plant was completed in 1996.
In 2007, a renovation of the surface of upper reservoir incl. improved sealing was performed by the Swiss company WALO Bertschinger.
In 2018, the original 7-blade runner was replaced with a new 9-blade runner with increased efficiency.
Manufacturers
Motor-Generator: Skoda Plzen (nowadays owned by Brush), https://www.brush.eu/front-page
Pump-Turbine: CKD Blansko, https://www.ckdblansko.cz/en/
Transformers: Skoda Plzen (ETD transformatory), http://www.etd-bez.cz/en
HV circuit breakers: ABB (nowadays Hitachi ABB Power Grids), https://www.hitachiabb-powergrids.com/
Figure 7 documents the transport of step-up block transformer from the manufacturer (ETD transformatory in Pilsen) to the power plant inside a cavern. Depicted is reload from rail to road transport in Kouty nad Desnou railway station.
Technical data of Dlouhe Strane
The power plant features two turbine-generator sets. The turbines are reversible and can operate in turbine mode (driving the electric machine as generator) or in a pump mode (driven by electric machine as motor).
Installed power: 2 x 325 MW
Average water head: 510.6 m
Diameter of pressurized water pipes: 3’600 mm
Length of pressurized water pipes: 1’500 m
Turbine type: Francis
Operator: CEZ
Power generation: 3’500 MWh/pumped cycle
Pumping time: 6-7 hours
Turbining time: 5-6 hours
Block step-up transformer: 22/420 kV
Switchgear: gas insulated (SF6)
A look into the machine room is shown in figure 9. It is the upper floor of the cavern. There are “pony” motors to start up the motor-generators (direct on-line start for machines of this size is not possible). Pony motor may be misleading as those machines have approx. 35 MW rating for short time.
Start-up time of the power plant is less than 2 minutes. The importance of Dlouhe Strane is not only for power storage and covering of peak demand, but also as a primary source after a blackout to restart the power grid.
Motor-Generator
Max. apparent power:
355.5 MVA (generator) / 353.0 MVA (motor)
Power at coupling:
320.0 MW (generator) / 330.0 MW (motor)
Rated current
9’329 A (generator) / 9’264 A (motor)
Rated voltage:
22 kV ±8%
Rated speed:
428.6 rpm
Pump-Turbine
Maximum water head:
532.7 m (turbine) / 554.2 m (pump)
Average water head:
510 m (turbine) / 534 m (pump)
Maximum flow rate:
68 m³/s (turbine) / 54.5 m³/s (pump)
Upper reservoir
– Rockfill dam
– Water volume 2’580’000 m³
– flooded area 15.4 ha
– crest length 1.7 km
– altitude approx. 1’350 meters above sea level
The climatic conditions in the upper reservoir are rather extreme. In winter the minimum temperature can be as low as -25°C while during sunny summer days the surface temperature of the asphalt layer reaches up to + 60°C.
Lower reservoir
– Earthfill dam
– Water volume 3’405’000 m³
– flooded area 16.3 ha
– dam height 56 m
– altitude approx. 825 meters above sea level
Transmission line
After a step-up transformer the power is transmitted through 400 kV line. That is the highest transmission voltage level used in the Czech Republic (220 kV and 400 kV).
Excursion tour at Dlouhe Strane
If you have a chance, we definitely recommend to visit Dlouhe Strane. CEZ operates a visitor centre there and a tour can be booked by anyone. The full excursion tour takes approx. 3 hours. During that time you will visit the power plant, watch two short movies: one about hydroelectric power generation and another one specific about Dlouhe Strane. You will also visit the cavern incl. machine room and transport tunnels. Finally, a bus brings you on top to the dam of upper reservoir where you can admire the water work itself, but also an amazing view on nearby mountain peaks.
Tours can be booked through this email:
The power plant can be visited throughout the year. However, the upper reservoir is not accessible during winter time because of climatic conditions.
If you are less interested in the excursion tour (which we really recommend – it is worth to visit) or just want to see the upper reservoir without visiting the machine room you can still use a new cable car that brings you few hundred meters higher in elevation. From there you can make several hikes and enjoy the nature in a protected area.
The power plant is remotely controlled from Prague as it serves as grid stabilizer. There are only few local workers performing some supervision and maintenance tasks. As the power plant is located in a protected landscape area, an electric car is a natural choice.
We hope to provide you at least little bit of impression about Dlouhe Strane pumped storage hydro power plant. Of course, it is not the same as visiting the site on your own. Maybe consider it as a tip for holidays or a longer weekend. You may also check out the virtual tour by following the ref. [3].
References
[1] CEZ Group, https://www.cez.cz/en/home
[2] Pumped hydro storage power plants – Introduction, https://mb-drive-services.com/pumped-storage-hydro-power-plants/
[3] Dlouhe Strane hydro-electric power plant – virtual tour, http://virtualniprohlidky.cez.cz/cez-dlouhe-strane-aj/
[4] BRUSH motor and generators, https://www.brush.eu/front-page
[5] CKD Blansko, https://www.ckdblansko.cz/en/
[6] ETD power transformers, http://www.etd-bez.cz/en
