The design of adjustable-speed pump-turbine modified from existing constant-speed on Okutataragi Power Station

Okutataragi Power Station, which has been operated since July 1975, is one of the largest pumped-storage hydropower plant in Japan. Nowadays, for the purpose of improving the economic efficiency, we decided to introduce 2 adjustable-speed pump-turbine units replacing existing fixed-speed ones. [1] We also decided to renew the pump-turbine runner at the same time. We designed the new turbines for not only corresponding to adjustable-speed system but also increasing the amount of generating electricity in middle-load operation by the efficiency improvement in partial load operation, and extending the range of stable operation at adjustable-speed mode. This paper introduces the design of pump-turbine runner.