The Lower Svir hydroelectric station was constructed 40 years ago in accordance with Lenin's plan for the electrification of Russia. The first generating unit was put into operation on December 13, 1933, and the last (fourth) on September 30, 1935. During the Second World War the station was damaged extensively and reconstructed in . The presence of Lake Ortega at the source of the Svir River, with a surface area of 9700 km 2 and useful storage of about 17 km 3, favorably affects the runoff regime. The total length of the Svir from the source to its discharge into Lake Ladoga is 225 kin; the drop of the river between the lakes is 27.5 In, including 26.5 m over rapids (to the site of the Lower Svir station).Two hydroelectric stations have been constructed on the Svir -Upper Svir and Lower Svir. A number of problems of shipping were solved by the construction of the sequence of hydroelectric stations on the Svir, which is a part of the most important transport lines of the Volga-Baltic and White Sea-Baltic waterways.The exceptionally complex and unfavorable geologic and hydrogeologic conditions were a special feature of the construction site of the Lower-Svir station.* The foundation bedrocks consisted of a variagated stratum of Devonian clays with thin (from 1.5 mm to 1.5-2 m) interlayers of sands and very soft clays overlain by saturated moraine deposits, enclosing quicksand here and there. Artesian waters entering from deep water-beating horizons are present ubiquitously in the Devonian deposits. The elevation of the free surface of these waters is 20-25 m higher than the elevation of the water level in the river. The Devonian clays and sand beds are extremely nonuniform in their density.
The Len~nergo system in Leningrad has six hydroelectric plants with a total capacity of 700 MW, which represents over 1.5% of the overaU capacity of this power system. The hydroelectric plants operate basically during the peaking portion of the load graph of the system, with one or two interruptions during the day. Under these operating conditions, there are regimen and technical output losses, caused by a decrease in the head and the efficiency as a resuk of regulation and of increased head losses in the trashracks. On the whole, in this power system the total energy losses at the hydroelectric plants amount to 6o7~ and their absolute value, even for the low-water years 1972 and 1973, exceeds 120 million kwh. The distribution of the additional energy losses at the different sources is as follows (according to data for 1972): in the trashracks, 1.3%; during daily regulation because of head drops, 2.2%; during regulation because of decrease in the efficiency, 0.25%; other losses (idle overflows, locking, seepage), 1.1%.Taking into account the increase in the daily regulation losses, caused by increase in the participation of the hydroelectric plants in regimen regulation the operating personnel of these plants and the Power Board focused considerable attention on reducing the technical losses, especially the head losses in the trashracks.Under the regimen exigencies of the power system, where basically a power effect and maximum participation in the covering of peak loads are needed from the hydroelectric plants, the head losses in the trashracks and the penstocks lead to an appreciable power reduction precisely during peaking operation, when maximum loads are placed on the hydroelectric plants and there are maximum discharges through the turbines. The high flow velocity and the rapid increase in the plant loads contribute to further intense obstruction of the trashracks. It follows that the problem of reducing the above-mentioned head losses is associated with the improvement of the operating flexibility of the hydroelectric plants and the increase in their participation in the regimen regulation.From the viewpoint of construction of the trashracks, the streams on which the I.en~nergo hydroelectric plants are located exhibit extremely dissimilar characteristics. For example, during the summer period, along the upper reaches of the Svir' River in the Ivinsk overflow of the reservoir for the Upper Svir' hydroelectric plant, large peat masses float and become peat islands, which are very harmful to hydroelectric plant operation. The Volkhov River, which flows through habitable and populated areas, carries during the flood period bushes, grass, construction debris, and different objects which obstruct the trashracks and bring up to 1.0 m and over the head loss through them. During the summer a large volume of grass is conveyed from the shallow Narva reservoir to the penstocks of the Narva hydroelectric plant. Under more favorable conditions, from the viewpoint of trashrack obstruction , are the Svetogorsk and Lesogor...
Six hydroelectric stations with an overall capacity of 670,000 kW, including the Lenin-Volkhov station, which was placed in service toward the end of 1926, the Lower Svir' station, which has been in service since the end of 1933, and the Lesogorsk station, which was introduced in 1937, operate in the Leningrad power s~tem. The structures and equipment of these three plants have been in operation for 48, 41, and 37 years, respectively; the equipmerit suffered partial damage during the Great Fatherland War of 1041-1945. The service lives of the Svir', Svetogot', Svetogorsk, and Narva hydroelectric power stations are also relatively long, andamount to 20-25 years. These circumstances predetermine the corresponding wear experienced by the equipment and structures, their aging in a technical sense, and the resultant need for reconstruction.Significant work on the rebuilding and modernization of the hydromechauical equipment and hydraulic structures, basic power equipment, electric circuits and apparatus, and auxiliary equipment has already been performed, and a large volume of technological and automatic-systems equipment capable of various technical decisions has also been installed in the hydroelectric stations of the Leningrad District Administration of Power Facilities (LDAPF).As a result of long-term operation, including the destruction and evacuation ordered during the Great Fatherland War and the subsequent reconstruction, the hydraulic turbine guide vanes at the Volkhov station were recently found to be highly worn, the runners had suffered significant erosion and corrosion, and the windings, iron stator mounts, thrust bearings, and other subassemblies of the hydraulic generators, and the eleciric equipment were found in poor condition; as a result of critical crane wear, it was prohibited from further operation, and the railroad turntable was shut down. After raising the intake level 2 m above the design level, the corresponding head increase on the turbines shifted the effective zone into a low-efficiency region (80-82~0 efficiency) with the units of the Volkhov station operating at rated capacity, while the mean weighted efficiency of modern hydraulic units reaches 87-88%. As a result of the wear on the turbine runners, the hydraulic units at this station are presently even less efficient, and the annual losses in electzic-powe~ generation are quite significant. This station has complex and obsolete electric circuits, particularly the supply circuits for internal requirements.In connection with an increase in the capacity of the power system and electric communications, a significant portion of the electrical apparatus does not accomodate short-circuit currents at the present time. Thus. the state of the equipment at the Volkhov station dictates the replacement of all basic and auxiliary equipment at some future date.
Under conditions of the dispersion of the load curve and unfavorable shifts in the structure of generating capacities with an increase in the proportion of poorly flexible equipment, the problem of increasing the hydroelectric-station manipulation in the power grid is urgent.The manipulative characteristics of hydroelectric-station equipment under conditions of intense regime regulation with frequent starts, stops, and load changes are determined in many respects by the operation of the thrust bearing, which is one of the most essential and vulnerable components of the turbo-generator unit. An increase of manipulation with participation of a hydroelectric station in regime regulation complicates the working conditions of the thrust bearings as a consequence of the frequent repetition of the indicated variable regimes. The majority of unit failures occur became of damage to the bearing under these regimes, whereupon the units are out of operation for a long time.An analysis of the data on the damage to bearings of large units (Volga-Lenin. Volga-22nd Party Congress, Bratsk, Krasnoyarsk, Votkir~ Saratov, Gorky, Dneprodzerzhinsk. and other hydroelectric stations) between 1960 and 1972 showed that of the total number of bearings damaged (157 cases), 51% were during starting, synchronization, load build-up, or soon after starting; 5% on stopping; ~o on change of load; 4@o on changing to a synchronous condenser (SC) regime or to an active regime; 5% on a change of head.
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