Voltage sags are momentary dips in voltage that may cause misoperations to the electric utility customers' sensitive loads. These misoperations may only be an annoyance to the residential sector, but, on the industrial and commercial front, they can cost millions of dollars each year. It is impossible to eliminate all of these faults and associated voltage sags, but an improvement can be achieved through power system modifications on both the utility system and the industrial or commercial power system. The evaluation of these system modifications was difficult in the past, but the authors describe a voltage sag analysis program, developed by Power Technologies, Inc., which has simplified the task. The program uses methodologies developed for the update of the IEEE Gold Book (IEEE Standard 493, Recommended Practice for the Design of Reliable industrial and Commercial Power Systems). The results of this sag analysis program form the basis of possible future cost-benefit analysis enabling electric utilities and utility customers to make the most economic system modification.
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