Overspeeding processes in reversible units of pumped-storage stations: Fid-Bau Portal

Overspeeding processes in reversible units of pumped-storage stations

Arshenevskii, N. N.

Conclusions 1. When a reversible unit enters an overspeed regime water hammer occurs, and the rotational speed when ns>270 rpm exceeds the overspeed rpm determined from the universal characteristic (if special measures against water hammer are not provided for: no-load releases, artificial braking, etc.), in connection with which a determination of the guarantees of regulation when designing a pumped-storage station should begin precisely with this process. 2. The process of overspeeding of a unit should be considered as emergency process and should be assigned to the case of unusual loading combinations. If the pumped-storage station has a group (branched) scheme of penstocks, then this process is examined only for one unit, and the others in the given group can: a) operate simultaneously with the power system; b) drop the load; c) be stopped. 3. The unit can be brought out of overspeeding: by an emergency slide valve connecting the appropriate cavities of the servomotors with the accumulator of the oil-pressure system with the receiver tank, by closing the quick-acting gates, by manual control, or by closing the bulkhead gates. It is possible to use these methods also in combination. When designing a pumped-storage station complete calculations of the indicated methods should be performed with consideration of the particular closing regimes and scheme of penstocks. 4. An analysis of the process of overspeeding should be continued both for mixed-flow and for diagonal- and axial-flow reversible machines.