Vibration monitoring is one of the

Vibration monitoring is one of the most promising methodsin a mechanical fault diagnosis [8], [9]. In [3] and [4],some effective parameters, including number, amplitude, andinterval of vibration bursts, are extracted from the vibrationof the OLTC using wavelet transform. Later, Li et al. [4]proposed a fault diagnosis method based on Markov chain.Meanwhile, to overcome the nonstationary property of OLTCvibration signals, phase-space reconstruction is introducedin a mechanical fault diagnostic of OLTC [6], [7]. So far,the existing methods are almost on the basis of statisticalanalysis. However, fault samples are often not easy to obtain.When fault signal samples are not enough, the accuracy rateof diagnostics may reduce. What’s more, how to distinguishdifferent degrees of failure is significant in the maintenance.Considering the complexity of OLTC’s inner structure, solvingthis problem is even harder.