A new current-based method for voltage sag source location using directional overcurrent relay information

SUMMARY When several utilities manage interconnected power networks, a voltage sag that occurred in the grid of one utility may affect the sensitive customers in other utilities. From this point of view, it is a major issue to find the source location of the voltage sags to impose penalties to responsible parties and improve mitigation strategies. With such worthwhile objectives, this paper presents a new method based on directional overcurrent relay information or by applying its algorithm at the utilities’ interconnection buses. In this method, the current (pre-sag and during sag) is the only variable which can be measured by relay/power quality monitor. Then, relative location of voltage sag source is determined using variation of measured positive-sequence current phasor magnitude and the sign of its phase-angle jump. The proposed method is compared with distance relay and phase change in sequence current methods on a sample network. This network is a large-scale actual regional network including transmission and sub-transmission levels, which is modeled by using PSCAD/EMTDC, and the output data are processed via MATLAB codes. The results show that the proposed method can effectively determine the location of voltage sag source under both symmetrical and asymmetrical faults, furthermore representing its unique applicability in cases where only current signals are recorded. Copyright © 2011 John Wiley & Sons, Ltd.