Regulation of the hydraulic units of the Nurek hydroelectric station without surge shafts in the headrace tunnels

Abstract

The Nurek hydroelectric station [1] is a peak-load station and will participate in automatic power regulation by means of a control computer installed at the dispatcher point of the integrated power system of Central Asia. The installed capacity of the station is 2,700,000 kW in nine units.The water-conducting structures of the station (three deep water intakes, three headraces with shafts for the emergency repair gates, three surge shafts, and nine penstocks to the station power house) are unique in their parameters (see Fig. 1 of [1]).Over their entire length the water-conducting structures (see Fig. 1) pass through fractured rock of average toughness which has been grouted around the conduits. To start up the first line of the hydroelectric station an intermediate intake was located 100 m below the permanent intakes and connected with the penstocks by a 6.5-mdiameter tunnel which divided by horizontal forks into three branches with a diameter of 4.5 m each. The shaft of the emergency gate, controlled from an underground room, was placed in the initial section of the intermediate tunnel.When working out the design of the Nurek hydroelectric station, the Central Asian Branch of the All-Union Planning, Surveying, and Scientific-Research Institute (Saogidroproekt) with the help of the Kuibyshev Moscow Institute of Civil Engineering (MISI) calculated* the unsteady regimes in the penstocks for the following equipment parameters (suggested by the plant): flywheel moment of the generator rotor, 21,500 tons; m2; maximum head in the spiral casing, not more than 380 m; temporary unsteady running of the units, not more than 57%.For the adopted scheme of the conduits with the fork located directly beyond the surge shaft, a simultaneous drop of the load from three units was used in the calculation, although in the given case the number of units dropping the load had practically no effect on the magnitude of water hammer. For r lv = 5400 m2/sec, control was guaranteed for a 57% temporary uneven running of the units and dynamic head of 365 m.During further planning, Saogidroproekt and MISI sought solutions which would eliminate the surge shafts. The following was the basis for this search: in the earlier design of the Charvak hydroelectric station the surge shafts were eliminated owing to the safety factors that existed in the water turbine used (developed earlier for another hydroelectric station), which made it possible to increase the design value of the dynamic head. The slight increase of the diameter of the headrace tunnels that was required proved to be economically justified. There is a tendency to increase the response time and magnitude of temporary uneven running of the units, which has found reflection both abroad [2] and in our country (e.g., in the design of the Kuban'-Kalaus hydroelectric stations). During development of the design of the generator of the Nurek station it was found that the flywheelmasses ofits rotor could be increased.The search for solutions was carried out in two directions: along the line ...

Advanced design solutions for underground structures at nurek hydroelectric station

“…As a result, grounds were established for deleting the surge shafts, provided the following conditions were observed: The flywheel moment of the generator rotor was increased to 24,000 ton-m = , the temporary irregular running of the turbogenerator was raised to 65%, and the adopted regulation period was made 12 sec. Deletion of the surge shafts resulted in a considerable saving [3].…”