VAMP Ltd
Feeder and motor manager
Technical description
VAMP 257
VM257.EN002
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39
2.3.10.
Undercurrent protection (37)
The three-phase undercurrent unit measures the fundamental
frequency component of the phase currents.
The stage I< can be configured for definite time characteristic.
The undercurrent stage is protecting rather the device driven
by the motor e.g. a submersible pump, than the motor itself.
Parameters of the undercurrent stage:
I< (37)
Parameter Value/unit Description
Measured
value
ILmin
A
Min. value of phase currents IL1
… IL3 in primary value
I<
xImode
Setting value as per times I
MOT
Setting
values
t<
S
Operation time [s]
SCntr
Start counter (Start) reading
TCntr
Trip counter (Trip) reading
1-N, 2-N
3-N
Fault type/single-phase fault e.g.:
1-N = fault on phase L1
1-2, 2-3
1-3
Fault type/two-phase fault
e.g.: 2-3 = fault between L2 and L3
Type
1-2-3
Fault type/three-phase fault
Flt %
Min. value of fault current as per
times I
MOT
Load %
1s mean value of pre-fault currents
IL1 … IL3
Recorded
values
EDly %
Elapsed time as compared to the
set operate time, 100% = tripping
2.3.11.
Directional earth fault protection (67N)
The directional earth fault protection is used in networks
where a sensitive earth fault protection is needed and in
applications with varying network structure and length.
The manager consists of versatile protection functions for
network earth fault protection. The earth fault current is meas-
ured via energizing input I
0
or I
02,
or the earth fault current can
be calculated from the phase currents internally. The residual
voltage is measured via energizing input U
0
(e.g. broken delta
connection), or it can be calculated from the phase voltages
internally according to the selected protection mode:
•
Phase: the residual voltage is calculated from the phase
voltages and therefore a separate residual voltage
transformer is not needed. The setting values are relative to
the VT secondary voltage (U
0sec
) defined in configuration.
•
Line+U
0
: The residual voltage is measured with voltage
transformers (e.g. a broken delta connection). The setting
values are relative to the VT
0
secondary voltage (U
0sec
)
defined in configuration.