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Fluke 434/435
Users Manual
9-2
Figure 9-2. Characteristics of a voltage swell
During an Interruption the voltage sinks well below its nominal value. In three phase
systems an interruption begins when the voltage on all phases are below threshold and
ends when one phase is equal to or above the interruption threshold plus hysteresis. The
trigger conditions for interruptions are threshold and hysteresis. Interruptions are
characterized by duration, magnitude and time of occurrence. Figure 9-3 explains this.
duration
time
magnitude
NOMINAL
VOLTAGE
INTERRUPTION-INT-
HYSTERESIS
0 VOLT
THRESHOLD
Figure 9-3. Characteristics of a voltage interruption
Rapid voltage changes are quick transitions of the RMS voltage between two steady-
states. Rapid voltage changes are captured based on steady voltage tolerance, steady time,
minimum step detected, and minimum rate (%/s). When a voltage change crosses the dip
or swell thresholds, it is considered a dip or swell and not a rapid voltage change.
Additional to detection based upon voltage step (Vstep), detection based upon maximum
voltage change (Vmax) can be selected when setting up the limits. Note that the
Norwegian FoL requires detection on Vmax. The event list shows the voltage step and
transition time. The detailed event list shows the Vmax relative to the nominal voltage.
Figure 9-4 explains this.