Voltage sags refer to brief reductions in root mean square (rms) voltage, primarily resulting from short circuits and the initiation of large motors. The significant concern surrounding voltage sags arises from the issues they create for various types of equipment. Notably, adjustable-speed drives, process-control systems, and computers are particularly vulnerable to these fluctuations. Certain devices may trip when the rms voltage falls below 90% for durations exceeding one or two cycles, leading to frequent disruptions-potentially occurring dozens of times annually. In the context of a paper mill's process-control equipment, the repercussions of voltage sags can be substantial. While voltage sags are not as detrimental to industrial operations as either short or long interruptions, their higher frequency means that the cumulative impact of sags can surpass that of interruptions. Additionally, addressing voltage sags presents considerable challenges.