Detection of Point-on-wave for Voltage Sags by Hilbert Complex Plane

Voltage sags are one of the common power qual-ity disturbances in electricity networks. Point-on-wave (POW) detection of voltage sag becomes crucial since it largely affects the operations of protective relays and mechanical contractors. This paper proposes a simple yet effective POW detection method targeting voltage sag events. By employing Hilbert complex plane, an absolute distance deviation profile is obtained to detect the exact initiation and recovery points of voltage sag. A simulation model is built to generate a number of sag events corresponding to various common causes. The model contains various network components and a high harmonic producing load. Detection accuracy of the proposed method is compared with conventional moving RMS method. Moreover, effect of various sampling rate is also considered on the detection accuracy.