Study On Vibration Characteristics Of Multi-Unit Segments Of Underground Hydropower House

Studying the vibration law of hydropower house structures and units is very important to guid safe operation of a hydropower station.In this paper,basing on the vibration prototype observation test,the interaction rule of multi-unit vibration and dynamic characteristics of the hydropower house was studied.The main contents and conclusions are as follows:(1)Through the analysis of the prototype observation data,the vibration effects of two unit-segments are complecated.The vibration frequency is related to low frequency of tailwater vortex,frequency conversion of hydraulic turbine,the water hammer frequency of the pressure piping system,non-uniform flow frequency of volute and the guide vanes.Vibration dominant frequency of transmission between lower structures of the plant and turbine units is tail water vortex frequency.Similarly,Vibration dominant frequency of transmission between floors and columns construction is non-uniform flow frequency of volute.(2)According to the results of the wavelet frequency-division of the vibration signals,we can know that intermediate frequency vibration affects the three unit-segaments,the dominant frequencies of which are non-uniform flow frequency of volute and the guide vanes;On the contrary,the vibration induced by tailwater vortex affects the four unit-segaments.(3)In the paper,the transfer process of the vibration influence between the unit-segments was analyzed through frequency-division of the vibration signals.It was found that the influence of the vibration of the tailwater vortex is transmitted not only through the foundation or the substructure of the plant,but also through the mutual interference between the tailrace systems of the power house.(4)In the stable operation of the hydropower station,the standard deviation of the vibration of the units and structures was compared and analyzed.It was founded that within a single unit-segment,there is the vertical amplitude amplification phenomenon in the middle floor slab and generator floor.So it maybe resonance between the non-uniform flows load of volute and floors.(5)In this paper,a dynamic parameter identification method for the hydropower plant structure is proposed,which is based on data fusion and LMD.Compared with digital filter,wavelet threshold and EEMD,this method has certain advantages in the identification of vibration signal dynamic parameters.The method can identify natural frequencies and damping ratioes of the hydropower house structure.