Voltage sags and interruptions in a distribution system

Abstract

Voltage sag is the important factor in power quality problem faced by many industrial customers. The most frequently reported among various types of power quality disturbance are voltage 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 is 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 caused by fault in distribution systems 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. Analysis of voltage sag is needed to know voltage sag characteristic, because the equipment sensitivity is influenced by the characteristic. This paper is also presents the calculation result of analysis of voltage sags that carried out in a distribution system model by using the software MATLAB.