VAMP 260
Power monitoring unit
Technical description
VAMP Ltd
14
Vamp 24h support phone : +358 (0)20 753 3264
VM260.EN004
Max3
%Un Maximum voltage value during
the sag/swell in the input 3
2.2.9.
Voltage interruptions
The unit includes a simple function to detect and measure
voltage sags.
The function calculates the number of voltage interruptions
and the total time of the voltage interruptions within a 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, 1
st
January 00:00 – 31
st
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 pre-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 U
1
<.
Whenever the measured U
1
goes below the limit, the
interruption counter is increased, and the total time starts
cumulating.
Shortest recognized interruption time is 40 ms. If the voltage-
off time is shorter it may be recognized depending on the depth
of the voltage dip, the ratio of the limit and the voltage value
before the dip.
If the voltage has been significantly over the limit U
1
< and then
there is a small and short underswing, it will not be recognized
(Figure 2.2.9-1).
Figure 2.2.9-1. Short voltage sag 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 2.2.9-2).
