A swell is defined as an increase to between 1 1 and 1 8 Pu in rms voltage or current at the power frequency for durations from 0 5 cycle to 1 minute The term "momentary overvoltage" is also used as a synonym for the term swell Like sags, swells are associated with system fault conditions but are not as common Swells can occur from the temporary voltage rise on the unfaulted phases during a single-line-to-ground (SLG) fault Swells can also be caused by switching off a large load or energizing a large capacitor bank and are characterized by their magnitude (rms value) and duration The severity of a voltage swell is a function of the fault location, system impedance and grounding