为了提取信号中较弱的故障特征频率分量，本文以正交小波为基函数，在对振动信号实施冗余小波变换分解的基础上，提出了一种等效的功率谱分析方法。该方法利用冗余小波变换分解提供的多分辨信息，先剔除高频噪声分量，在获得其他尺度的功率谱后，对其进行归一化处理。由于每个分解频带的分析频率相同，因此叠加归一化的功率谱得到信号的等效功率谱，使被淹没信号中的微弱频率分量在功率谱上显现出来。采用这种方法有效地提取了烟汽轮机汽封与转子之间摩擦故障的特征信息。

In order to extract weak fault features from vibration signals efficiently, an equivalent power spectrum analysis approach is proposed which applies the Redundant Wavelet Transform (RWT) decomposition by using an orthogonal wavelet as a basis function. The new approach makes full use of multi-resolution information obtained by the RWT decomposition. Firstly, noise component in high-frequency-band is omitted, and the other decomposition components are treated as useful components to calculate their power spectrum respectively. Then a normalized operation is made for these power spectrums. Because the analytic frequency of the RWT decomposition components is the same, the equivalent power spectrum is gained by adding the normalized power spectrums. As a result, some weak frequency components that submerged in the signal before are revealed on the equivalent power spectrum. The proposed approach has been used to diagnose friction fault between gas-seal and rotor of a gas turbine in an oil refinery and detected the fault features effectively.