Latest newsThe Grande Dixence reversible pump-turbine goes under the HYDRO microscope

The Grande Dixence reversible pump-turbine goes under the HYDRO microscope

The HYDRO team recorded performance measurements for the reversible pump-turbine at the Grande Dixence pumping station at the foot of the Mattertal. The primary objective of calibrating the flow was exceeded by adding a proposal to optimise the working of the machine.

An extensive performance measurement exercise was conducted on the reversible pump-turbine of Z’Mutt pumping station in 2024. Located at the foot of the Mattertal at an altitude of 1,972 metres, it is the most powerful station within the Grande Dixence complex. The centre recently had a new variable-speed pump-turbine installed, which allows it greater flexibility. Although the variable speed is beneficial in operational terms, it has added a lot of complexity in general.

Calibrating the flow measurement system

Having been made operational, the flow measurement system via the differential pressure method (Winter-Kennedy) had to be calibrated. This sort of job is tailor-made for HYDRO, as we possess the required skills and know-how. Our experts used the thermodynamic method to ascertain the real flow and calibrate the measurement system in place.

Precision and perseverance

Semiconductor strain gauges were attached to a free shaft opening to help us learn more about the performance of the variable-speed electric machine. A telemetry system was used to retrieve the signal from the rotating part. This very accurate torque measurement enabled us to determine the mechanical power and, therefore, the mechanical efficiency. A job of clockwork precision was performed on this 5 MW machine. On returning to the office following many attempts on site through the night, the company’s experts got to grips with the vast volume of data processing, and the flow measurement was calibrated. Finally, with their detailed knowledge of the workings of pump-turbines, solutions were also proposed for expanding the machine’s operating capacity.

HYDRO’S DNA

Rigorous measurement is a delicate and essential exercise, but applying the data to benefit the owner is where HYDRO’s measurement experts really excel. It’s in our DNA.