Construction of finite impulse wavelet filter for partial discharge localisation inside a transformer winding

Abstract

In high voltage (H.V.) plant, ageing processes can occur in the insulation system which are totally unavoidable and ultimately limit the operational life of the plant. Ultimately, partial discharge (PD) activity can start to occur at particular points within the insulation system. Operational over stressing and defects introduced during manufacture may also cause PD activity and the presence of this activity if it remains untreated will lead to the development of accelerated degradation processes until eventually there may be catastrophic failure. Therefore, partial discharge condition monitoring of valuable HV plant such as a transformers and in particular along a transformer winding is an important research area as this may ultimately provide asset health information enabling the maintenance and replacement processes to be carried out effectively. Wavelet multi-resolution analysis consists of a series of quadrature filter banks which are associated with a high pass and low pass filter. The process is performed in order to decompose original signals into different levels that contain different time-frequency resolutions of the original waveform. Thus, the spread of signal energy over different time/frequency ranges can be determined. The use of system identification in the frequency domain using the Wavelet transform provides unique selections of the particular frequency range of interest of the measured PD signals that have propagated inside a transformer winding. Wavelet decomposition levels can be combined linearly with Principal Component Analysis (PCA) and this may provide useful information about the location of the discharge source within the winding and with further implementation using an infinite impulse response (IIR) filter approximation, it is possible to construct a standard filter based on the Wavelet transform and PCA that can be implemented as an automatic PD localization tool. © 2013 IEEE.