Hydraulic transient challenges for the upgrade of FMHL+ pumped storage power plant from 240MW to 420MW

Abstract

The FMHL power plant was originally a 240 MW pumped-storage power plant in Canton Vaud, Switzerland, which installed capacity was recently extended to 480 MW with maximal output power set to 420 MW including 60 MW as reserve. This project, named FMHL+ consists in developing a new powerhouse to be operated in parallel to the existing powerhouse and connected to the same waterways. Increasing the output and input power of an existing hydroelectric scheme from 240 to 420 MW using existing headrace tunnel and pressure shaft with maximum gross head of 878 mWC is a challenging task as far as the hydraulic transients are concerned. The paper first presents the FMHL+ project and the challenges resulting from the significant power increase in turbine and pumping mode of operation and the technical solutions selected to accommodate this power increase. Then the paper presents the Real-Time Simulation Monitoring and the related power plant modelling used to perform the transient tests. Finally comparison between simulation results and on-site measurements resulting from the Real-Time monitoring will be presented for the hydraulic transients tests of emergency shutdown in turbine mode at 428 MW and for emergency shutdown in pumping mode at -420 MW performed. The good agreement between simulation results and measurements enabled to confirm the appropriate hydraulic transient behavior of the new surge tank and its effectiveness in protecting the headrace tunnel against water hammer pressure waves.