The Pyotr Neporozhny Sayano-Shushenskaya hydroelectric power plant is located on the Yenisei River in the Sayan canyon in south-eastern Khakassia. It is the uppermost dam in the Yenisei River hydroelectric power plant complex and one of the world's largest power plants, with an installed capacity of 6,400 MW and an average annual output of 22.8 billion KWh.
The head at the Sayano-Shushenskaya power plant is formed by a 242-metre arch-gravity dam with a base width of 105.7 metres and a crest width of 25 metres. The crest length of the arch-gravity dam is 1074.4 metres.
This unique arch dam - which was designed by the Leningrad branch of the Hydroproekt Institute (Lengidroproyekt) to withstand Siberia's severe temperatures and the width of the Yenisei River - is unparalleled in the world.
The power plant houses 10 water turbines with a capacity of 640 MW each. The spillway dam, located on the right bank of the Yenisei River, is 189.6 metres long, has 12 sections and 11 underwater races, with a maximum spillway capacity of 13,600 cubic metres per second.
The dam supports the Sayano-Shushenskoe reservoir, which has a total capacity of 31.3 cubic kilometres, a useful capacity of 15.3 cubic kilometres and a surface area of 621 square kilometres.
Construction of the plant began on April 2, 1963. A cofferdam was built across the Yenisei River in October 1975 in order to build the dam.
The Sayano-Shushenskaya dam is a unique hydraulic facility both in terms of size and the complexity of its construction. The high-pressure arch-gravity dam has no parallels in Russia or abroad. It is one of the world's tallest dams.
The dam's stability under the pressure of 30 million tons of water is provided by the facility's own weight (60%) and by the upper arch belt (40%), which transmits its load onto the rocky left and right banks at a depth of 15 metres and 10 metres, respectively.
The plant's hydro power equipment was manufactured by the Leningrad Metal Plant LMZ and Elektrosila, both now part of the company Power Machines. A water turbine with a capacity of 640 MW, a nominal voltage of 15,750 watts and an operating speed of 142.8 rpm was built by Elektrosila under the supervision of chief engineer Alexander Dukshtau.
The generators at the Sayano-Shushenskaya hydroelectric power plant have the following characteristics:
Total weight: 1,860 tons
Maximum installation weight: 890 tons
Stator external diameter: 14,800 mm
The plant is equipped with РО-230/833-0-677 water turbines operating at an average head of 194 metres of water with a maximum head of 220 m.
On August 17, 2009, a massive accident at the station damaged or destroyed essential equipment and left 75 dead. The accident led to changes in safety standards at hydroelectric power stations. All new power stations will have life-support systems that operate largely automatically. The plant is equipped with a closed circuit video monitoring system consisting of 11 cameras recording the condition of hydraulic units' main terminals, the upstream hydraulic lock control mechanisms, the generator covers, as well as stator barrels and dam overfall watershed abutment.
Repair work at the dam is currently in full swing. The effort involves 2,508 people and 91 units of equipment. In 2009, a total of 6.4 billion rubles were allocated for the repairs, with an additional outlay of 16.1 billion rubles in 2010. Repair work is financed solely by RusHydro, the operator of the power station.
In 2009, an 11.7 billion-ruble equipment supply contract was signed with Power Machines. All water turbines are scheduled to be replaced by 2014. Plans call for the first unit (water turbine and generator) to be manufactured in January 2011, with a new unit being manufactured every four to six weeks from that point on. The company will manufacture six new water turbine units in 2011. The remaining equipment will be manufactured in 2012.
A considerable amount of repair work has been completed since the disaster. As a result, water turbine units 5 and 6 - which were the least affected by the accident - were restarted during the first quarter of 2010. Units 3 and 4 are scheduled to begin operating by the end of this year.
The power plant is scheduled to resume operations in 2014 after all water turbine units have been replaced.
Following the accident, the Sayano-Shushenskaya power plant became the world's first dam to operate in winter without functioning water turbines as a result of the installation of additional water passage points and measures taken to prevent icing.
On June 1, 2010, during peak flooding of the Yenisei River, the company plans to put the first part of the coastal spillway into operation. With a carrying capacity of 2,000 cubic metres per second, the spillway will considerably decrease the load on the service spillway dissipating basin and increase safety.
Construction of the coastal spillway began in 2005. Following the accident, a decision was made to speed up construction so that the spillway will be operational by summer 2010. During the first six months of 2010, construction workers will cast 135,000 cubic metres of concrete, build 12,100 cubic metres of tunnels, remove 408,000 cubic metres of rock and assemble 328,300 tons of hydro power equipment and facilities.
Currently, 2,586 employees are working round-the-clock to build the spillway. This work is supported by 3 concrete batching and mixing plants, 5 column cranes, 12 crawler and truck-mounted cranes, 10 concrete pumps and 21 concrete mixers.
In order to speed up construction, two additional concrete pumps will be added by the end of February, and the number of construction workers will rise to 3,000. In March, the fourth concrete batching and mixing plant will be started up to provide enough concrete for the casting work planned for spring.
An inspection of the dam's hydraulic facilities carried out one month after the accident by a commission of Russia's leading hydraulic engineers and representatives from Lengidroproyekt and the industrial safety watchdog Rostekhnadzor revealed that the accident did not affect the safety and performance of the hydraulic facilities of the Sayano-Shushenskaya hydroelectric power plant or the Mainsky hydroelectric complex. The commission ruled that the dam poses no threat to the people residing in the lower pool area and that the operating level meets current regulatory requirements. The inspection also revealed that the plant's dam foundation system is in normal operating condition, with no changes in the position of the GA1-GA10 foundation blocks recorded either before or after the accident.
As a result of prolonged freezing temperatures in early winter, a thick layer of overflow ice formed on the dam facilities, which many considered a threat to the dam's stability. At temperatures below -15C, a cloud of mist rises above the spillway basin to heights of 100 to 200 metres before falling as snow on the overfall dam's crest and platform. This resulted in a two-meter-thick wall of ice and snow at an elevation of 430m - 340m on the spillway joint piers covering the water flow, which did not prevent water passage but lowered vapor density.
When temperatures were at their lowest, a layer of ice build-up and snow also formed on the crane trestle, amounting to 100 tons per running meter, while the maximum weight is 400 tons. These ice build-ups have a friable structure and are continuously eroded by the water passing through the spillway.
Large amounts of bischofite, or crystalline salt, are being used for de-icing. Seventy hot-air heaters with a total output of 1.5 megawatt have been installed under the machinery hall roof to prevent icing. Maintaining temperatures above zero also prevents an ice cover from forming on the outside surface of the facility and makes it easier to physically remove the ice.
In 2010, a multipurpose fire engine equipped with a unit producing thermally activated water was used to combat icing. The vehicle was developed by specialists at the Russian Emergency Ministry's State Fire Service Academy and the company Aqua-Pyro-Alliance. During the first few days of uninterrupted work, the engine was effective at removing snow and ice build-up. The dividing wall crest was completely cleared of ice and snow. Ice is being removed by a group of specialists from the Emergency Ministry and industrial climbers. In late January 2010, the ministry's emergency crew and fire safety research institute removed the layer of ice and snow off the crest using compressed air jacks.
The condition of the dam has been inspected several times over the past six months. In February 2010, the Expert Commission was set up to examine the Sayano-Shushenskaya dam's foundation system. Of 26 commission members, 10 are independent experts. The commission was set up partly in response to widespread public attention and partly by the desire to use leading hydraulic engineers to evaluate the supporting capacity of the dam foundation and the need for additional measures to ensure its durability and safety.
Currently, all hydraulic engineering installations and mechanical equipment at the Sayano-Shushenskaya hydroelectric power station, with the exception of the facilities and equipment destroyed or damaged in the accident, are in operating condition. The dam's operating level meets current regulatory requirements and ensures reliability and safety.