李家峡水电站机组开停机过程非平稳振动信号的小波分析

基于李家峡水电站双排机组振动的现场试验研究，并且针对传统频谱分析方法傅立叶变换（FFT）对于非平稳信号已力不从心这一缺陷，利用小波分析方法在时域和频域上同时具有良好的局部化性质，通过对开停机这一典型非平稳过程信号进行小波及小波包分析，将其分解到不同频带内，获取微弱信息和提取优势频率，并对其作振源分析，得出开停机初始时刻因水流不稳均出现强烈的振动现象，且低频段信号能量最大，开停机过程水流脉动压力和尾水涡带摆动是引起定子基础振动的主要原因。同时也证明了小波是处理非平稳信号的最有力的工具。

Analysis on unsteady vibration signal wavelet during starting up and shutting down process of hydropower units in Lijiaxia Hydropower Station

In light of the limitation of Fast Fourier Transform(FFT) for the method of traditional spectrum analysis to analyze the unsteady signal,wavelet and wavelet analysis are made for the typical unsteady process signal of starting up and shut down with the good characteristic of simultaneous localization in both the time and the frequency domains based on the field test on the vibration of two-row placed units in Lijiaxia Hydropower Station,in which the signal is decomposed into different frequency band,and then the weak signal is caught and the dominant frequency is picked up for the analysis of the vibration source.The analysis demonstrates that the intense vibration phenomenon,with the maximum signal energy of the low frequency band,normally caused by the unsteady flow in the initial stage of the starting up and shut down,and the main cause of the vibration from the stator foundation is the fluctuating pressure and the turbulent flow of the tail water during the starting up and the shut down;at the same time,the wavelet is proved to be a most powerful tool for processing the unsteady signal concerned.