Operating experience and suggestions on reconstruction of the turbines of the Dnepr-I hydroelectric station

Conclusions

• 1. A generalization of the 40-year operating experience shows the need to reconstruct the turbines of Dnepr-I for the following reasons: the present operating conditions markedly differ in head from the design ones, as a result of which the efficiency of the turbine in the main load regimes is 5–8% lower than the optimal; owing to the numerous welds of the blades during repair of cavitation erosion, deformation of the blade system has occurred, which reduced the maximum value of efficiency of the turbines by about 1.5%; the existing runners are obsolete in comparison with those developed in recent years; there is a steady tendency toward a decrease of the reliability indices of the equipment.

• 2. Calculations on a computer for selecting the optimal parameters (turbine power and speed) of a new turbine when reconstructing the hydrostation were carried out in conformity with the actual operating conditions. On the basis of the criterion of the maximum weighted average efficiency, on the new turbine it is expedient to have: n_s=88.2 min⁻¹, N_t=74.0 MW at H=35.5 m, η=94.8%. On the basis of the criterion of obtaining a maximum power, on the new turbine it is expedient to have: n_s=90.9 min⁻¹, N_t=78.0 MW at H_O=35.3 m, η=94.5%.

• 3. To increase the efficiency and operating reliability of the existing equipment (before its reconstruction), it is recommended to limit the power of the turbines by means of the opening of the gate apparatus.