Uprating of 325 MW pump turbine at PSPP Dlouhé Stráne

Pump turbines were installed at pumped-storage hydroelectric power plant Dlouhé Stráne in the Czech Republic in 1996. After almost 20 years of operation the owner and operator of the pumped-storage plant ČEZ decided upon the uprating of the first unit TG1. The reason for this decision was a forthcoming lifetime expiration of the runner, caused by high dynamic loads of the pump turbine unit operation. The second reason evocating the uprating process was the request for a wider operation range especially in generating mode and, of course, the improvement of the total efficiency of pump turbine cycle. The principle was to solve the uprating with a replacement of the existing runner by a new one. Development of the new runner with expected higher reliability was supported by an effective cooperation among hydraulic and mechanical designers. The procedure of runner replacement with higher capacity and higher efficiency is described in details. The hydraulic design of the new runner was approved during model acceptance tests. The manufacturing process and installation of the new runner is mentioned. The new technology for the runner fabrication from two pieces is presented. Finally after installation of the new runner the on site efficiency measurement has been carried out and results will be presented in the proposed paper.