“…As suggested in [6][7][8][9][10][11][12][13], a partial discharge phenomenon can be characterized in most cases by the partial discharge phase, mean discharge number, mean discharge, mean discharge frequency, and so on, and the commonly seen approaches for defect pattern recognition include Fourier transform, Discrete Fourier Transform, Hilbert-Huang Transform (HHT), etc. Although the embedded characteristics can be extracted directly from partial discharge signals, a large database is required when statistics are performed on the characteristics of interest over a long time span.…”