Diversion of stream through hydroelectric stations with high dams during construction

1. The scheme of diverting the flow according to steps of construction of especially high dams is the basis of the site organization plan and also has a substantial effect on the design and layout of the main structures of a hydrostation. 2. The best scheme of constructing a dam is that for which stream diversion is carried out through one level of spillways, which later is used as the service level. If it is impossible to accomplish this scheme, it is necessary to provide the possibility of operating a lower level of spillways until the higher level is completely ready for passing the flow, including floods. Schemes calling for “fleeing from water” should be completely eliminated. 3. Designs of spillway gates of high dams, including the materials used in them, should be tested on simpler and less important structures. The layout of even temporary gates should provide the possibility of repair of the movable parts and seals. 4. The configuration of the spillway channels and the location of the regulating gates should be designated so as to eliminate or limit the possibility of the occurrence of conditions for the development of cavitation processes. The best solution in this case is to locate the regulating gate at the outlet of the pressure part of the spillway. 5. The scheme of dissipating the energy of the flow in a stilling basin at heads of more than 120 (140) m also has substantial shortcomings complicating the preparation of the structures for stream diversion by steps of construction.