Characterizing the diverter switch of a load tap changer in a transformer using wavelet and modal analysis

Vibration analysis is a promising technique in the diagnosis of the OLTC in power transformers. In this paper the vibration modes of the natural frequencies of the diverter switch cylinder, the head, and the disc of the moving contact of an OLTC in good condition are obtained by modal analysis of the numerical model. The obtained frequencies are identified with real vibration signal analysis recorded with a mono-axial piezoelectric accelerometer on a vertical axis. The actual vibration signals were processed using a Hilbert transform and a discrete wavelet transform. This article proposes using the natural frequencies of the modes of vibration calculated for the numerical model of 3 OLCT elements as the pattern for identification of the frequencies generated in the analysis of the experimental vibration signal.The diverter switch cylinder, the head, and the disc of the moving contact of an OLTC were designed in commercial software SolidWorks™. Natural frequencies were analyzed using a numerical model with commercial software of the finite element method (MEF) Algor™ with 6 degrees of freedom (DOF) at each node.