Digital identification of voltage sag in distribution system

Voltage sags in distribution system occur more frequently and devastatingly than other power quality problems. Voltage sags due to line faults, transformer energizing and induction motor starting are the main interference sources. The reasons leading to these sags are analyzed and simulation result are presented by an EMTP model in this paper. A new identification method to sag waveforms is presented in this paper, since B-spline wavelet transform is good at the analysis of singularity. The characteristics of sag waveform are extracted easily and accurately by using the B-spline wavelet transform.