An automatic voltage sag detector using a discrete wavelet transform and a CFAR detector

The authors present a novel algorithm for a voltage sag detector on transmission and distribution lines. A wavelet transform is utilized to extract voltage sag disturbances from a fundamental 60 Hz sinusoidal wave, and a SG-CA CFAR (stop-and-go cell average constant false alarm rate) detector detects the starting and ending time of the voltage sag. Based on this result, they calculate precise sag duration for both transmission and distribution lines. This algorithm is tested using actual data and the results are compared with previous hard threshold-based wavelet sag detector.