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9-1
Chapter 9
Dips & Swells
Introduction
Dips & Swells records Dips, Interruptions, Rapid Voltage Changes, and Swells.
Dips (Sags) and Swells are fast deviations from the normal voltage. Magnitude may be
ten up to hundreds of volts. Duration may vary from a half cycle to a few seconds as
defined in EN61000-4-30. The Analyzer allows you to choose nominal or sliding
reference voltage. A sliding reference voltage uses measured values filtered with a 1-
minute time constant.
During a dip the voltage drops; during a swell the voltage rises. In three phase systems a
dip begins when the voltage on one or more phases drops below the dip threshold and
ends when all phases are equal to or above the dip threshold plus hysteresis. The trigger
conditions for dips and swells are threshold and hysteresis. Dips and swells are
characterized by duration, magnitude, and time of occurrence. Figure 9-1 and 9-2 explain
this.
Figure 9-1. Characteristics of a voltage dip