3.4 Voltage interruptions
3 Supporting functions
Technical description
90
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VM55.EN005
3.4.
Voltage interruptions
VS_VoltageInts
The device includes a simple function to detect voltage
interruptions. The function calculates the number of voltage
interruptions and the total time of the voltage-off time within a
given calendar period. The period is based on the real time
clock of the device. The available periods are:
8 hours, 00:00 – 08:00, 08:00 – 16:00, 16:00 – 24:00
one day, 00:00 – 24:00
one week, Monday 00:00 – Sunday 24:00
one month, the first day 00:00 – the last day 24:00
one year, 1st January 00:00 – 31st December 24:00
After each period, the number of interruptions and the total
interruption time are stored as previous values. The
interruption counter and the total time are cleared for a new
period. The old previous values are overwritten.
The voltage interruption is based on the value of the positive
sequence voltage U
1
and a user given limit value. Whenever
the measured U
1
goes below the limit, the interruption counter
is increased, and the total time counter starts increasing.
Shortest recognized interruption time is 40 ms. If the voltage-
off time is shorter it may be recognized depending on the
relative depth of the voltage dip.
If the voltage has been significantly over the limit U
1
< and then
there is a small and short under-swing, it will not be recognized
(Figure 3.4-1).
Figure 3.4-1. A short voltage interruption which is probably not recognized
On the other hand, if the limit U
1
< is high and the voltage has
been near this limit, and then there is a short but very deep
dip, it will be recognized (Figure 3.4-2).
