“…Some examples are fast Fourier transform method [3], fractal-based method [4], S-transform method [5], time-frequency ambiguity plane method [6], short time power and correlation transform method [7], wavelet transform method [8], Hilbert transform method [9], and Chirp-Z transform (CZT) method [10]. Neural networks (NNs) [11,12] with different structures are traditionally used as classifier but recently probabilistic neural network (PNN) [2,13] and support vector machines (SVMs) [14][15][16] are introduced as new learning machines which are more effective. Hidden Markov model [17], rule-based expert system and fuzzy logic have also been employed at the decision-making step in the process of classifying PQ disturbance types [18,19].…”