Putting into operation the first small hydroelectric station with pumps and motors as turbines and generators in the Commonwealth of Independent States

The Dobromyslyansk small hydroelectric station (HES) on the Chernitsa River with a capacity of 200 kW in two units was connected to the "Vitebsk Power" association system on April 2, 1993, after reconstruction and reequipping. The station operated in the original form from 1962 to the end of the 1970s. At it were installed two units with RO123V-84 Francis turbines in open free-flow turbine pits. At a design head of 5.6 m the HES developed a capacity of about 200 kW. The powerhouse is of the channel type with two unit blocks. The concrete spillway dam with three 5-m-wide spillways is calculated for a discharge of 262 m3/sec. The upper edge of the gates is located at the elevation of the normal pool level (NPL) of the reservoir. By 1989, when the question arose about reconstructing the Dobromyslyansk HES, all equipment at it was dismantled, and the turbines that were left were not suitable for repair. The concrete members of the powerhouse were in a satisfactory condition, which gave grounds to use them further. The main problem consisted in the absence of small hydraulic turbines and generators for a capacity of 100-150 kW and heads of 4-6 m. The variant of equipment with a Pr20/811-V-100 turbine produced by the Syzran Turbine Plant and a synchronous generator examined in the technical and economic calculation was rejected owing to the high cost of the equipment and absence of guarantees of its timely delivery. The use of quantity-produced pump units as turbines and induction electric motors as generators made it possible to solve the problem of equipping the station. Such a solution had an advantage both in cost and time of delivery. In essence, it was the only real solution both from an economic and technical viewpoint. Data on the cost of variants of equipment of the Dobromyslyansk HES in 1990 prices are given in Table 1. Quantity production of the pump units set up by the Ural Hydraulic Machinery Plant (Uralgidromash) and Ural Electrical Heavy Machinery Plant (Ural61ektrotyazhmash) made it possible to equip the station with cheap and reliable electrical equipment providing sufficiently high power indices. According to the data of model power tests of the pump impellers in turbine regimes [1], their efficiency in a wide range of heads is 75%, which is lower than for turbines. However, as a comparison of the variants showed, such a decrease of efficiency is compensated by the low cost of the pump equipment, which is cheaper than turbine equipment by an order. The theoretical aspects of the operation of induction electrical machines in a generator regime are known. It is sufficient that the speed due to the action of the hydraulic torque of the turbine be higher than the synchronous speed. The electrical machine should be excited from the supply line or from a special large-capacity capacitor bank if the station is operating for an isolated consumer. A capacitor bank is used also for compensating the consumption of reactive power. The equipment of the Dobromyslyansk small HES was chosen on the basis of the "Provisional recommendations on the use of pump units as power equipment of small hydroelectric stations" [1] developed by specialists of the Department of Hydropower Utilization of the Moscow Civil Engineering Institute (MISI). The highest-speed OP16 impeller was chosen with consideration of a maximum head of 5.6 m at the HES. The existing dimensions of the unit blocks made it possible to install two units with OV 16-87-MK pumps and VAN 118/28-12UZ induction motors.