Characteristics of the processes of load dropping by diagonal-flow reversible turbine-pump units of pumped-storage stations

Conclusions

• 1. The obtainment, as a result of numerous calculations on a computer, of generalized relations of the main indices of the load dropping process in the field T_W/T_u−T_W/T_S makes it possible at the initial design stages to rapidly analyze the decisions made about the parameters of pressure conduits and pump-turbines and regulating regimes.

• 2. By virtue of the peculiarities of the universal characteristics of reversible diagonal-flow pump-turbines, the maximum value of the temporal nonuniformity of the operation of the unit during load dropping in real ranges of the constants of inertia of the conduits and unit does not exceed the allowable standard value β_max=n_max/n₀=1.6.

• 3. The search for efficient regulating regimes reducing water hammer facilitates the introduction of the new concepts “initial” and “final” water hammer and plotting the corresponding zones on generalizing graphs.

• 4. Rotating the runner blades of the diagonal-flow pump-turbines along with closing the gate apparatus after dropping the load is favorable for reducing water hammer. In this respect they can be more preferable than reversible mixed-flow pump-turbines for the same values of the heads, T_W/T_S and T_W/T_u.