An Online Method of Extracting Single Event Sag Indices

Utilities require a high storage capacity to characterize voltage sag on the power system network. The RMS has limited capability and can only acquire event magnitude and duration information. In this paper the authors propose a measurement technique based on instantaneous tracking of the amplitude phase and frequency of a non-stationery sinusoid. From the tracked parameters, the amplitude, duration and phase angle shift of the sag event is determined. This is especially useful for fault finding or recreating sag events. The proposed method is simple to implement on a signal processor and was successfully tested in simulation.