In today's liberalized markets, customers have the opportunity to choose the utility based on the quality they serve, thus increasing the importance of energy quality objectives. It is therefore necessary to quickly quantify PQ disturbances and analyze them, leading to an accurate assessment of power quality indices. Power quality disturbances are mainly of two categories, stationary and non-stationary. Stationary signal is one whose frequency and amplitude do not vary with time, while non-stationary signal is one whose frequency, amplitude or both vary with time. Most power quality disturbances that occur are non-stationary in nature and noisy due to the dynamic nature of the system operating conditions. Therefore, there is a need for a technique that can accurately decompose the non-stationary power signal and which should also provide time and frequency information. The definitions recommended in IEEE 1459-200 [1] and [2] are used to evaluate power quality indices. However, these indices are based on the fast Fourier transform which ...