VAMP 257
Feeder and motor manager
Technical description
VAMP Ltd
88
VAMP 24h support phone : +358 (0)20 753 3264
VM257.EN002
2.4.6.
Current transformer supervision
VAMP257 supervises the external wiring between the relay
terminal and current transformer secondary connection, as
well. Furthermore, this is a safety feature, since an open
secondary of a CT, causes very dangerous voltages.
CT supervisor measures phase currents. If one of the three
phase currents drops below I
min
< setting, while another phase
current is exceeding the I
max
> setting, the supervisor will issue
an alarm after the operation delay has elapsed.
Setting parameters of CT supervisor:
CTSV ( )
Parameter Value
Unit Default Description
Imax >
0.0 … 10.0;
xIn 2.0
Upper setting for CT
supervisor
Imin <
0.0 … 10.0;
xIn 0.2
Lower setting for CT
supervisor
t>
0.02 … 600.00
s
0.10
Operation delay
CT on
On; Off
-
On
CT supervisor on event
CT off
On; Off
-
On
CT supervisor off event
Measured and recorded values of CT supervisor:
CTSV ( )
Parameter Value
Unit
Description
ILmax
A
Maximum of phase currents
Measured
value
ILmin
A
Minimum of phase currents
Display Imax>,Imin<
A Setting values as primary
values
Date
-
Date of CT supervision alarm
Time
-
Time of CT supervision alarm
Imax
A
Maximum phase current
Recorded
values
Imin
A
Minimum phase current
2.4.7.
Voltage transformer supervision
VAMP257 supervises the external wiring between the relay
terminal and voltage transformer secondary connection, as
well. If there is a fuse in the voltage transformer circuitry, the
blown fuse causes that the relay cannot measure voltages.
Therefore, an alarm should be issued. Furthermore, in some
cases, the protection functions that are using voltage signals,
should be blocked to avoid false trippings.
VT supervisor measures phase voltages and currents. Then it
calculates the negative sequence voltage (U
2
) and the negative
sequence current (I
2
). If the U
2
is more that the U
2
> setting and
at the same time, I
2
is less than the I
2
< setting, the supervisor
will issue an alarm after the operation delay has elapsed.
