Voltage sag and the sensitive load

Abstract

Voltage sag is the important factor in power quality problem faced by many industrial consumers. The most frequently reported among various types of power quality disturbance are voltages sags. The disturbance will cause the sensitive load/equipment (adjustable speed drive, contactor starter in motor, etc. to drop out. The main source of voltage sags are faults on the utility system and motor starting. Voltage sag caused by faults are generally more severe than those caused by starting. Voltage sag is normally characterized by a magnitude and duration. The load sensitivity is generally determined by the both values. The sag magnitude is depending on fault location and fault type. The sag duration depends on the clearing time the protective device used. This paper discusses estimation of voltage sag cause by fault in distribution system that supplied to the sensitive load and sag duration can be controlled using protective device. The result shows that the faults on the adjacent sensitive load are more severe and sensitive load protected by protective device characteristics with longer operating time will most likely to drop out.