Characterisation of Vibration Signals Using Continuous Wavelet Transform for Condition Assessment on On-Load Tap-Changers

Abstract

The operation of an on-load tap-changer (OLTC) on a high-voltage power transformer produces a vibration signal that consists of a series of well-defined transients. Due to the harmonic and non-stationary nature of transient vibration signals, the traditional frequency and time–frequency techniques are not effective for characterising this type of vibration signal. The time domain features such as delays in time between transients, and the number and strengths of transients are more important for the assessment of the OLTC condition. This paper details the development of an OLTC vibration signal characterisation technique using the continuous wavelet transform (CWT). The CWT, due to its capability of multi-scale localisation in the time domain, is an effective tool in extracting the essential features from the original signals. These features are utilised to provide reliable indications of the health of the equipment. Signals from real plant are used to demonstrate the usefulness of the proposed technique.