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In this paper Application of an Empirical Wavelet Transform based technique is proposed to estimate time-varying PQ indices for accurate assessment of Power Quality Disturbances. The EWT approach mainly aims to extract the actual fundamental frequency component and disturbance components from any distorted signal. The empirical wavelet transform consists of two major steps: detect the Fourier supports, and build the corresponding wavelet accordingly to those supports; filter the input signal with the obtained filter bank to get the fundamental component and disturbance components. Since the extracted components contain only one frequency component, Hilbert transform is utilized to estimate the instantaneous frequency and amplitude information, from this information we can estimate time-varying PQ indices. The proposed method is employed to assess successfully all sorts of Power Quality Disturbances such as voltage sag, swell, interruption, transients, harmonics, spikes, notches etc. From the results we can say that the proposed method detects disturbance start time, end time, duration of existence and its content more accurately.