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2.6 Overvoltage and Undervoltage Protection
91
7ST6 Manual
E50417-G1176-C251-A3
on/off. The overvoltage protection is blocked as soon as the signal
„Dis. PICKUP“
is activated.
Both stages of the overvoltage protection have a separately settable grading margin
for the TRIP command of their respective stage.
2.6.2
Undervoltage Protection
The figure below shows the logic diagram of the undervoltage protection.
Figure 2-21
Control and pick-up/tripping logic of the undervoltage protection
With the parameter
3711
UNDERVOLTAGE
the undervoltage protection can be
switched
ON
or
OFF
. The indication
„UNDER. OFF“
is output when the function is
switched on/off.
The undervoltage protection is blocked when at least one of the signals
„Dis.
PICKUP“
or
„Failure Umeas“
is active. The signal
„Failure Umeas“
prevents
the undervoltage protection from picking up when the measuring voltage fails. The un-
dervoltage protection is also blocked when the current drops below a set threshold of
0.05 I
n
.
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