Power Quality Practice Test

Voltage sags are the most common power quality disturbance because brief drops in voltage happen frequently from everyday operations on the distribution network. When large motors start, transformers energize, or loads switch on and off (and during short faults or capacitor switching), the voltage on feeders dips briefly. These events occur regularly, so sag events show up more often in utility and customer disturbance data than other types like interruptions, transients, or swells. That’s why the statement is true. The other options imply uncertainty or a lower frequency, which doesn’t align with the typical survey findings that sags dominate as the most frequent disturbance.