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The voltage interruption is based on the value of the positive
sequence voltage U
and a user given limit value. Whenever the
1
measured U
goes below the limit, the interruption counter is
1
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
there is a small and short under-swing, it will not be recognized
(Figure 4.2).
Voltage U
1
U <
1
10
20
30
Figure 4.2 – A short voltage interruption which is probably not recognized
On the other hand, if the limit U
near this limit, and then there is a short but very deep dip, it will be
recognized (Figure 4.3).
Voltage U
1
U <
1
10
20
30
Figure 4.3 – A short voltage interrupt that will be recognized
Supporting Functions
40
50
60
70
80
< is high and the voltage has been
1
40
50
60
70
80
4-9
< and then
1
Time
90
(ms)
VoltageSag1
Time
90
(ms)
VoltageSag2
857-UM001A-EN-P – July 2009
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