VAMP 257
Feeder and motor manager
Technical description
VAMP Ltd
58
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VM257.EN002
5.
The CB closes. The CloseCB output relay opens, and the
discrimination time from shot 1 starts. The current is still
over the I> setting.
6.
The discrimination time from the shot 1 runs out; the
OpenCB relay output closes.
7.
The CB opens. The dead time from shot 2 starts, and the
OpenCB relay output opens.
8.
The dead time from shot 2 runs out; the CloseCB output
relay closes.
9.
The CB closes. The CloseCB output relay opens, and the
discrimination time from shot 2 starts. The current is now
under I> setting.
10.
Reclaim time starts. After the reclaim time the AR
sequence is successfully executed. The AR function moves
to wait for a new AR request in shot 1.
2.3.17.
Overvoltage protection (59)
The three-phase overvoltage function consists of three
separately adjustable overvoltage stages (stage U>, U>> and
U>>>).
The overvoltage function measures the fundamental frequency
component of the line voltages. The protection stages operate
with definite time characteristics.
The function starts if the actual value of any phase exceeds the
setting value. If an overvoltage situation continues after the
operation time has elapsed, the function trips.
The overvoltage stages have a fixed start delay. If a delayed
alarm about a voltage fault is required, a settable start delay
and trip time can be obtained by combining two stages. See
Figure 2.3.17-1. Both the stages detect the overvoltage, but the
start signals are ignored. The trip signal of stage U> is used as
an alarm signal, and the trip information from stage U>> is
used for the actual trip. The overvoltage setting value for stage
U>> has to be higher than the setting value for stage U> to
ensure an alarm before trip.
Overvolta
g
e fault
U>
start
U>>
start
U>
tri
p
U>>
tri
p
ALARM
T
RI
P
Figure 2.3.17-1. Settable start delay is obtained by combining two protection
stages
