Abstract: Jixi pumped-storage hydropower station is the first hydropower station employing pump-turbine units with splitter blades developed by the domestic manufacturer, thereby catching attentions from many parties. During the commissioning of its first unit, several research teams conducted comprehensive tests on its running stability, including shaft run-outs, stationary component vibrations, and pressure pulsations.This paper employs the method of tracking the time-domain peak-to-peak values as well as using the spectrum technique in frequency domain to analyze the measured data, and discusses the characteristics of unit stability in different working modes﹣stable pumping operation, stable generating operation, pump mode startup, and turbine mode startup under load increasing. The testing results indicate that in stable running conditions, all the peak-to-peak values of the shaft run-out and stationary vibration are in Zone A of the specifications, thus meeting the requirements of safe operation. A pump-turbine unit with splitter blades has much more complicated frequency spectra of pressure pulsations in comparison with a routine Francis pump-turbine. In stable on-cam running of pump mode, dominant frequencies at certain measuring points vary with water head. For the startup processes of pump mode and turbine mode, the unit stability parameters meet the requirements of operation.

Key words: pump-turbine, stability analysis, splitter blade, rotor-stator interaction, short-time Fourier transform