In the modern industrial world most electronic and electrical control devices are characterized by an extreme sensitivity on power quality variations. Voltage sag is defined as a short duration reduction in voltage magnitude and is considered to be the most serious power quality issue. The accuracy limits of an index used for predicting the magnitude and duration of voltage sag caused by an increase in power demand due to induction motor starting is investigated in this paper. The index accuracy is tested for various amounts and types of loading as well as load and distribution line X/R ratios. The result is the definition of the accuracy limits of the proposed index, which enhances the power quality of a system, through accurately predicting the voltage sag in terms of both magnitude and duration.
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