Cam Correlation Analysis Using Acoustic Discharge Measurement

The low head hydro power plant in Wettingen, Switzerland, is in operation since 1933 and no effective cam optimization has been carried out up to now. The goal of the measuring campaign was to provide data enabling an economic study for a retrofit and upgrade project of the plant and the measurement of the efficiency improvement of turbines after refurbishment. The contribution discusses cam tests using the acoustic transit time method in the intake for discharge measurements. A cam correlation analysis and an efficiency test of the installed Kaplan turbines were performed as a first measurement campaign showing the actual status. While one turbine operated at optimum cam, the other two turbines operated off-cam. After rehabilitation works, based on the recommendations of the first measurements, a second measurement campaign was performed. The results showed the expected efficiency increase due to overhaul of the regulating mechanics (connection between the piston stroke in the machine hall and the regulating ring / guide vane stem at the turbine) of the governor. With the set of data from the second measurement campaign an optimization study for the operation of the three Kaplan units were conducted. Especially the transition zone from one to two and from two to three machine operation could be optimized due to the knowledge of the individual efficiency curves.