Water passage regime and the condition of the spillway dam
Water inflow to the dam at the Sayano-Shushenskaya HPP is 2,950 cubic meters per second, and water is released through the spillway portion at a rate of 3,325 cubic meters per second. Nine of the spillway dam bays are open to the second degree and two of them are open to the first degree. The level of the upper pool and the release of water through the hydro-engineering structures at the HPP station fully comply with the water release regime recommended by the Angaro-Yenisei Basin Water Administration, appropriately adjusted in the operating mode. The upper pool level is 537.57 meters (compared to a normal headwater level of 539 meters), and this level is dropping by 3 - 5 centimeters per day. Currently, the lower pool level is 324.62 meters.
The 500 kW outside switchgear has live voltage. Repair workers at the Sayano-Shushenskaya HPP are receiving power from the reserve transformer to supply and meet the switchgear-500's own needs. Cranes operating at the upper pool are being powered from an electrical power sub-station at the shore spillway construction site, with 0.4 kW being fed to the upper pool cranes in the usual manner.
Five 6/0.4 kW transformer sub-stations have been set up and connected in the area of the HPP's turbine room (three times 400 kWA and two times 630 kWA), as well as two 6/0.4 kW Package Transformer Sub-stations that have been set up at the end of the turbine room in the vicinity of hydro-turbine 10. A 35/6 kW transformer has been connected near the transformer area of block No. 5 and power has been supplied to busbars Sh-1 and Sh-3. Street lighting has been switched on at the site next to the station, as well as in the work zone in the turbine room.
A 10 MWA sub-station is being set up. The Õ26 circuit-breaker panel for its own needs is being reviewed and the 6/0.4 KW T67 and T68 are being dried out. Work is currently under way to restore the –6 and –8 switch and control gears and the direct current board which feeds the H17 transformer sub-station. Work has also begun on restoring the Õ2 and Õ3 boards to satisfy its own needs. High voltage testing is being carried out on the –10, –8 and –6 switch and control gears, as well as on the Õ26 and Õ30 boards and the Sh-2 busbar.
Power is now running to section 2 of the P-1 direct current board in the HPP's turbine room from the P-3 direct current board (using outside switchgear-500).
State of principal equipment
Based on the results of a visual examination, the accident completely destroyed hydro-turbines 2, 7 and 9. Turbines 1, 3, 4 and 10 have sustained damage to individual parts, while turbines 5 and 8 were somewhat damaged. Turbine 6 is in satisfactory condition.
Transformer groups 1T and 2T were damaged, but transformers 3T, 4T and 5T remain in satisfactory condition.
Current repair work
At present, work is under way to restore power equipment to a sufficient level to meet the HPP's own needs, and work is also continuing on clearing all dried out levels of the HPP's structure. Water is still constantly being pumped out of the power station's building.
At the time when the accident occurred on August 17th, 2009, nine of the Sayano-Shushenskaya HPP turbines were operating (while hydro-turbine No. 6 was in reserve). The total active capacity of the turbines totaled 4400 MW. At 4:15 Moscow time, a tremendous banging noise was heard in the turbine room, and the noise was followed by the release of a column of water around hydro-turbine No. 2. Light and sound alarms went off on the Central Control Console. Loading was reduced to 0 MW with a complete loss of power for the plant's own needs and flooding occurred in the building housing the turbine room.
At 5:20 Moscow Time, emergency repair valves on the inflows to the hydro-turbines were closed by hand from the crest of the dam and water access to the turbine room was cut off from the upper pool. To replace water passing through the turbines into the spillway dyke, at 7:32 Moscow Time, current was switched on from a mobile diesel generator on the gantry crane at the dam crest. By 7:50 Moscow time, the operation to lift the gates and release water was completed. During the entire course of the accident, there was no risk of water spilling over the top of the dam and the entire water inflow into the HPP's dam was released through the site's water release arches.
Intensive search-and-rescue and urgent accident restoration work is currently underway at the site.