Sayano -- Shushenskaya hydroelectric power station is geographically located on the Yenisei River, near Sayanogorsk in Khakassia, Russia. It was the largest hydro electrical power plant in Russian and sixth largest hydro electrical power station in the world, until the accident has occurred. The plant was operated by RusHydro, which was established in December 2004 during Russia's privatization movement, however about 60% of its shares are owned by Russian government. The milestone of RusHydro operation was that it has recorded the satiation's all-time highest electricity output in 24 hours (RusHydro, July 2009). RusHydro has 55 hydro plants with the installed capacity of 25.4 GW. The annual energy generation recorded by Sayano-Shushenskaya hydroelectric power station was about 23.4 TWh, which was almost one-quarter of that produced by RusHydro's resources for the Unified Energy Systems of Russia and Siberia. The major consumer of the plant was United company Rusal's aluminum smelters, that consumes about 70% production of RusHydro. The United Company Rusal's aluminum smelter produces about 12% of the world's aluminum (Boyko, A. & Popov, S. 2010)
Sayano -- Shushenskaya hydroelectric power disaster and its causes
The 2009 Sayano -- Shushenskaya hydroelectric power station accident occurred on 17 August 2009, when turbine 2 of the Sayano -- Shushenskaya hydroelectric power station was viciously burst. The damages were, turbine hall and engine room were flooded, the ceiling of the turbine hall collapsed, 9 of 10 turbines were destroyed, and total of 75 people were killed in this accident. The operational consequences were, the entire plant output capacity, adding up to be 6,400 MW and a considerable share of the supply to the local market, was lost, leading to widespread power failure in the local area, and compelling all major users like aluminum smelters to change to diesel generators. An official report on the accident was issued on 4 October 2009.
The disaster was felt initially with the loud noise from turbine 2. The turbine cover shot up and the rotor that weighs around 920 tones also shot out of its seat. This has made water to rush out from the cavity of the turbine into the machinery hall. Consequently the machinery hall was flooded. The disturbance in the plant has alerted the alarm received at the power station's main control panel. The failure of power had made total blackout in the premises (Izvestia, 2009). The rescue majors taken during the incident was that the steel gates to water intake pipes of turbines were manually closed, emergency diesel generator was started and the opening of spillway gates of the dam (RusHydro (August 2009). It was found that 75 people had died during this incident. (ITAR-TASS, September 2009)
Cause of accident
The accident was fundamentally caused by the turbine vibrations that had led to the serious damage of the turbine 2 and its cover. The precise cause of this vibration was investigated as most likely to be due to the huge volume of water from the Yenisei River flooded the turbine room thus causing one of the transformer explosion and widespread damage to all ten turbines. It was observed during the investigation that min 6 nuts were missing from the bolts securing the turbine cover. However, industry has viewed the cause of this accident as an inaccurate start-up process of the turbine that has consequently caused the hydraulic pressure surge. The vibration in turbine 2 was experienced since 10 years and was well-known by the company. It is also commented by industry specialist that its common practice in the industry to increase profit by reducing maintenance cost, investment on safety measures and training cost. To hide their mismanagement and ignored response on the maintenance of the plant, vibration in the turbine 2 was ignored by the company personnel and they have underestimated the adverse effects of its damage (Expert online, 2009).
According to Alexander Toloshinov, the former director general of the plant, the accident was due to the manufacturing defect in the turbine. According to him the construction of the turbine blades for such type of turbine is not reliable and possesses the risk of breaking down during operation. RusHydro has disapproved all the accusation that the dam outflow had overwhelmed the machinery hall thus leading to the damage of turbine 2. The management had tried to convince by saying that the dam outflow is seasonal and the displacement between the anchor legs and machinery hall has never exceeded 2.3 mm which is quite less than the width between them. Therefore it was not possible for damn to overwhelm the machinery hall. News has also reported the rebel party in Chechnya to be responsible for the blast as a confrontation on economic war on Russia. However they were refused by the authorities and were termed as nonsense and idiotic claims on rebel groups (Akin, Melissa August 2009). To directly claim who was responsible for the accident was pretty much controversial and complex. Investigation on the accident has shown the construction defects and manufacturing defaults in the huge power plant was the sole reason for this accident and the rescue measures adopted by the plant was not as immediate as it should have been.
After the accident 49 bolts were found from which 41 were damaged. It was found during investigation that the fire was caught at the hydroelectric power station of Bratsk. This fire has caused damage to the communication system and the automatic driving system of the power station. Rakurs, the company that had designed the automatic safety system of the plant had tried to safe its position by clarifying that the failure of the turbine 2 had let automatic shutdown system of the water intake pipes' gates (Titova, Irina August 2009).
Hydro Plant Re-Operational Strategy
The operational and environmental damages caused by the accident were reported to be:
a) Flooding of Turbine 6
b) Electrical damage and flooding of Turbine 5
c) Electrical and mechanical damage on the middle level in turbine 3 and 4
d) Turbine 2, 7, 9 were complete destroyed with enormous damage to the structures around it.
e) The damage of the power plant has resulted in the complete blackout of the premises as well as the surrounding areas that also include residential areas in the nearest localities.
f) The adverse impact of the accident can be seen by the oil spill on the river damaging the wildlife whose damage has not yet measured and destroyed the cultivated trout in the nearby riverside.
Restructuring and rebuilding of the Russian's largest power plant may take the time over than expected by the engineering and rebuilding teams working on the project. The equipment supplier to Russia, JSC Power Machines was assigned the task of supplying the company with the ten new turbines, nine generators and six new excitation system with the total cost of 11.7 billion rubles that sum up to be USD 392 million. These measures were taken to get the power plant in operation again with its fullest capacity and premium performance. According to Igor Kustin, the general director of power machines, the manufacturing process will further investigate the matter and will look into the real cause of the disaster which can be mitigated in the future developments (Ray, R.W March 2010).
The operational plan of the plant was that it initially aimed at restoring four units in 2010. The re-operational process would involve 2,508 workers and 91 pieces of equipment. During the manufacturing of the units following strategic decision were taken for proper functioning and risk minimization of the power plant:
a) The operational building of unit 5 and 6 will require 1,280 MW capacities and it assures minimum flooding risk thus providing regular stream of water supply to the residents and industrial operations with the needed electricity in the concerned areas.
b) With the setting up of the unit 6, 3 and 4 in operation the total planned capacity of the power plant in 2010 will be recorded to be 2,560 MW.
c) The structural repair which was under process was the repair of machinery hall, heating system, and electricity supply and sewage tunnels.
d) The spill way work is in continuous operation, therefore special consideration was given to establish the methods for preventing the dam from icing. (International Water Power and Dam Construction, September 2009)
The working Schedule of the operational process of the power plant can be tabularize in the following table 1 below:
Table1: Operational Schedule of the Sayano -- Shushenskaya hydroelectric power station
Power plant was trying to resolve the problem of dam icing. All 11 spillway gates were open and 70 heat guns with the approx output of 1,500 kW were installed to prevent hall form icing.
26 November 2009
Prepared dismantling of turbines 1,2,3,4,7,8,9 and 10. By this time only turbine 5 and 6 were repaired in their working place. The power plant has the plans to replace rest of the turbines with the modernized versions.