Adaptive Threshold for Segmentation of Combined Power Quality Disturbances

This paper proposes a method based on Wavelet Transform to determine an adaptive threshold to be used in the segmentation of combined disturbances related to Power Quality. This method is based on the decomposition of electrical signals that contain combined disturbances and uses the calculation of energy and entropy of energy of the second level of decomposition, obtained by Wavelet Transform, to determine an adaptive threshold. The proposed method was applied in signals generated by mathematical models, which contain combined disturbances of voltage sag with flicker, voltage swell with flicker, voltage sag with harmonics, voltage swell with harmonics, transient with voltage sag and transient with voltage swell. The results obtained so far evidence the possibility of identification and temporal detection (initial and final points) of disturbances with adequate accuracy, allowing better segmentation of the signals under analysis.