Aerial view of the Střekov hydro power plant
The Střekov power plant is part of the Střekov lock/reservoir built in 1932-1935. The entire waterworks is a Czech technical monument.
The power plant itself commenced its operation in 1936. The power plant’s total installed capacity is 19.5 MW and it features three vertical Kaplan turbines. The electricity it produces in a year would cover the consumption of more than 14,170 households, i.e. such towns as Jablonec nad Nisou or Česká Lípa.
The power plant is used permanently rather than during peak hours only. Střekov is the last but one artificial dam on the Elbe before it reaches the North Sea. The Střekov dam creates a reservoir 19.5 km long and impounds 16 million cubic metres of water.
Today, the main purpose of the Střekov waterworks in Ústí nad Labem is electricity generation as well as ensuring sufficient water depth and conditions for navigation. In addition, the waterworks allows safe fish pass.
Through the Elbe gorge
The aerial view of the landscape around the Masaryk Lock in Střekov shows a portion of the Elbe gorge upstream of the city of Ústí nad Labem. The city can be clearly seen in the north, together with its St Mary Rock, the Dobětice housing estate, Erbenova vyhlídka (420 m), the Střekov railway station and the railway bridge. The western and southern directions provide views of the romantic slopes of the Elbe Hills between Větruše and Vrkoč. The wooded slopes under Vrkoč conceal the 12-metre tall Vaňov waterfall, the most beautiful waterfall in the České Středohoří. There is the romantic vantage point named “Lovers” above a bend in the Elbe and also the Vaňovský vrch (561 m). However, we instinctively seek the most beautiful views on the other bank, with Střekov Castle on a rock. The castle was built in the early 14th century at the order of John of Luxembourg to protect ships on the Elbe and today it is a cultural monument, freely accessible throughout the year and owned by the Lobkowicz family. On the same bank, the valley up the river is bordered by the peaks of (left to right) Vysoký Ostrý (587 m), Malý Ostrý (571 m), Široký vrch (659 m), Trpasličí kameny (671 m) and Skřivánčí vrch (625 m) above the Brná district of Ústí nad Labem.
The waterworks – lock and weir – was constructed to make the Elbe shorter and navigable. The Střekov Rapids used to be a navigator’s nightmare and prevent any navigation in that stretch when flow rate was low. That is why the history of the Střekov waterworks starts in 1921, with the Committee for Vltava and Elbe Channelling in Bohemia of the Land Political Administration in Prague presenting a proposal for “navigation lock No. XI on the River Elbe at Střekov, combined with a hydro-electric power station” on 18 February 1921. The hydro-electric power station resulted from the fact that the construction of a dam created sufficient head, so this first proposal already envisaged use for power generation.
The construction of the lock started in 1923 and the river was diverted to the large lock in 1926 so that the construction of additional weir piers could proceed. It was decided to build a run-of-river hydro plant at the waterworks, which would run its turbines based on a daily hydrographic forecast to generate electricity and thus cover practically all costs associated with the construction of the waterworks.
The power plant was installed by ČKD Blansko, ČKD Praha, Škoda Plzeň and Křižík Praha. Subsidies from the state budget were provided in stages, which also explains the rather long total time of construction. The total cost of technology and work was CZK 22,936,078.
The hydro power plant was put into test operation in late 1935. After the start-up of the turbines in January 1936 and six months of test operation, the power plant commenced full operation in the second half of that year. Before the Nazi occupation, the power plant and the lock were administered by the Land Authority in Prague, with Central Electric Works appointed as manager for 20 years after commissioning. During the occupation, the power plant was operated by Berlin-based Elektro-Werke A. G. In 1943, the German state and Elektro-Werke A. G. concluded a lease contract with a flat-rate yearly rent of 375,000 Reichsmarks. The power plant was operated under these conditions until the end of the war.
Its operation remained largely uninterrupted throughout the war and the German staff positioned there remained in place until May 1945, when a decision of the National Council in Prague placed the power plant under the administration of Central Electric Works. It was found out during the handover that no construction work was performed during the occupation except for the construction of air-raid shelters in the turbine hall, control room, intake building and at the transformers. The air-raid shelters were removed because they impeded operation. The machinery and electric systems were in good and working order.
On 26 September 1955, Elektrotrust Most, n. p. was appointed the operating administrator of the power plant. The Střekov hydro power plant thus became a plant of the national enterprise Elektrárna Trmice. After Severočeské energetické závody in Děčín came into existence in 1963, the power plant was transferred to that enterprise, under direct control of the distribution plant in Ústí nad Labem, becoming an inherent part of its Operations department. After the state-owned enterprise Severočeské energetické závody were transformed into the joint-stock company Severočeská energetika in 1994, the power plant remained included in the organizational structure of the Ústí nad Labem plant. In 2007 the hydro power plant was transferred under a new owner, ČEZ Obnovitelné zdroje, s.r.o. Hradec Králové.
In 2006 CEZ Group finished a power plant upgrade, during which all turbines were overhauled and their operation was automated with a new control system. The reconstruction reduced the negative environmental impact of the power plant’s turbines because some lubricated equipment was replaced with lubrication-free equipment In addition, a wastewater and sewage water treatment plant was put into operation. The total investment in the hydro plant upgrade was CZK 167 million.
The emergency gate of one of the three Kaplan turbines was overhauled in the summer of 2008. The emergency gate slab, over seven metres high and weighing 65 tonnes, which closes the turbine intake and serves as a sluice gate, was removed from its shaft.
Hydro power plant operation
Three vertical Kaplan turbines with a total installed capacity of 19.5 MW were installed at the power plant. All equipment of the power plant, weir and locks is built for an upper pool level of 143.00 m above sea level. Since the roads on the banks were not rebuilt, the operating rules allow a level of 141.80 m. The Střekov dam thus creates a lake 19.5 km long, containing 16,500 m3 of water. Dam dimensions were proposed with respect to catastrophic flow rates in the Elbe, which were up to 5,500 m3 per second, and a minimum flow rate of 35 m3 per second. The turbines were sized for 300 m3 per second, which are available for about 4 months every year, with less than 300 m3 per second for 6 months and more than 300 m3 per second for 2 months.
The first overhauls of all three turbo-generator sets were performed by power plant personnel on their own, without the aid of any external companies. The first revision of TG 3 was performed in 1949, after 85,394 hours of operation. Finding out that the overall wear of the whole plant was minimal, it was decided to postpone the revision of another turbo-generator until 1954. TG 1 was overhauled in that year after 122,497 hours of operation and TG 2 was overhauled in 1956 after 134,269 hours of operation. Perfect maintenance in the next years was rewarded with trouble-free operation. To reduce the station service consumption, the uneconomical rotating generator exciters were replaced by a thyristor exciter assembly at each generator, including 10kV voltage regulation in 1972.
The second overhaul of the turbo-generator sets, including generators, was performed at the hydro plant in 1981-1990, with two sets always remaining in operation and one set shut down. The turbines were taken to ČKD Blansko after dismantling, where the formed cavities were welded up. The installation of new stator and rotor windings, including temperature sensors, was performed by Škoda Plzeň. The building’s roof was reconstructed in 1990-1991, including copper roofing. A repair of the control room, the control panel for control and signal cables, was started in 1992. A repair of the cable gallery between the power plant and its substation was performed in 1994, including the replacement of power cables between the generators and transformers. The emergency gates of all three generators were repaired in the same year, including the replacement of fine racks and baffles. The turbine hall’s roof cladding was also repaired. The “Power Plant Automation” project implemented in 2002-2005 included overhauls of the turbines and the installation of a new control system that makes the plant operation automatic.
Střekov hydro power plant with a fish ladder
The gates block the Střekov hydro plant’s outlets. There is a waterway running around the power plant’s building from the lower water level to the upper water level for upstream fish migration. Water from the upper level is routed in front of the fish ladder, where it ripples the surface and guides fish to the ladder. The fish ladder was built during the construction of the power plant itself. However, it became unusable and was upgraded in 2002, especially because of salmon.
The entire waterworks is a Czech technical monument. It consists of Masaryk Locks and a hydro power plant. The locks were built in 1920 to facilitate navigation on the Elbe. Then the power plant was added. The hydro power plant was put into operation in 1936. It's still the original structure in its entirety. It was one of the most advanced hydro power plants in Central Europe at its time.
The power plant is controlled from the control room or from the turbine hall, where control panels are located at each turbine. The Elbe River Authority manages the power plant’s output with respect to flow rate regulation in the Elbe. All three turbines usually work in winter while only one or two work in summer when flow rates are low.
The maximum usable head is 8.2 m, the minimum head is 3 m. A minimum output of 1 MW is needed for reliable turbo-generator operation; if it is lower, the power plant is shut down.
There are three Kaplan turbines in the turbine hall. The tapering hub can be seen on the shaft. It is a fast coupling of the Kaplan turbine shaft and the generator rotor shaft. The coupling is also the joint plane. Under the shaft you can see the top of the guide wheel, which regulates water flow at the Kaplan turbine. There is the spider at the top, with an axial and a radial bearings from which the assembly is suspended. The upper guide bearing is located at the oil head above the generator and the lower guide bearing is located above the runner of the Kaplan turbine.
Each turbine has its oil management system, adjuster pumping unit and hydraulic brakes. The adjuster pumping unit is an adjuster that controls the opening and closing of the guide wheel, the runner and the hydraulic brakes. Pumps draw oil from the lubrication oil tank and deliver it to the individual bearings of the turbine or the generator set. The oil then returns back, circulating in a closed circuit.
Peek into the turbine
The Střekov power plant structure allows an interesting peek into the “levels” of each of the three generator sets. All three have an installed unit capacity of 6.5 MW. The view of the upper level shows the “spider” from which the generator’s rotor is suspended. A coupling transfers energy from the lower part of the set, which the turbine receives from the water flowing underneath. That is concealed under the turbine cover at the lower level.
Above the turbine hall
Emergency gate rods
The emergency gate is a 6-metre, 60-tonne slab located upstream of each of the three turbines. It is used to seal the turbine, for example during emergencies (critical turbine speed, leak through the turbine guide vanes).
Střecha strojovny je umístěna venku.
At the racks
The power plant’s canal is separated from the river with a rack bridge. The rack bridge consists of a track for the rack cleaner, baffles and trash racks. The baffles trap debris floating on the surface of the Elbe. The racks, located underwater, are vanes that prevent debris from entering the hydro plant’s canal. The cleaner cleans the racks to prevent clogging and reduction of water flow through the power plant, which would cause different levels in the river and in the canal.
VThe outdoor substation transforms 22 kV to 10 kV in two transformers and power from the power plant is supplied by overhead wires to the 22kV Koštov substation or by a cable line to Střekov and Ústí nad Labem. The lines are managed from a regional control centre in Děčín.
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