PROJECT TITLE :

Time–frequency analyses of leakage current waveforms of high voltage insulators in uniform and non-uniform polluted conditions

ABSTRACT:

This study deals with the analysis of the leakage current (LC) in each time and frequency domains, for various configurations of polluted high voltage insulators (i.e. for clean and polluted insulator surfaces). The characteristic parameters of the recorded LC waveforms up to flashover particularly the peak value, the part shift, the entire harmonic distortion and the harmonic contents are investigated. It is shown that the LC peak value and therefore the section shift cannot be a trustworthy indication of the surface activity connected to partial discharges and waveform kind whereas the harmonic elements magnitude will be well correlated with the LC distortions; it is shown that in the first stages, the fifth and seventh harmonics contribute to the distortion of the LC whereas for advanced stage, the third harmonic contribution is the most significant. A time–frequency analysis is additionally applied to better perceive the LC behaviour. The spectrogram of the various stages of LC activity is computed using Matlab toolbox. The results show that point–frequency analysis can be used as a tool for patterns recognition and classification of the LC.