Figure. 5.4.19. - 93. Distance protection characteristics and directional overcurrent.
When above mentioned criteria are met, voltage memory will activate. VMEM will use “VMEM
activation voltage” as voltage amplitude even, when actual measured voltage has decreased lower or
close to nothing. Used angle is captured a moment before the fault has occurred and voltage memory
has been activated. When VMEM is activate, a speci c output “Voltage memory on” is switched on.
This signal can be found under device IO matrix.
Voltage memory blocking signal can be found among other stage related settings in “VT Module (3/4U)
1” -menu. In the blocking element the block signal is checked in the beginning of each program cycle.
Measured input values
Function block uses analog voltage and current measurement fundamental frequency RMS values.
Table. 5.4.19. - 160. Analogic magnitudes used by the Voltage angle memory function.
Signal
Description
Time base
IL1RMS
Fundamental RMS measurement of phase L1/A current
5 ms
IL2RMS
Fundamental RMS measurement of phase L2/B current
5 ms
IL3RMS
Fundamental RMS measurement of phase L3/C current
5 ms
U
1
RMS
Fundamental RMS measurement of voltage U
1
/V
5 ms
U
2
RMS
Fundamental RMS measurement of voltage U
2
/V
5 ms
U
3
RMS
Fundamental RMS measurement of voltage U
3
/V
5 ms
U
4
RMS
Fundamental RMS measurement of voltage U
4
/V
5 ms
Voltage measurement mode 3LN and 3LL use three voltage inputs channels U
A
, U
B
and U
C
. When
voltage mode is set to 2LL only two channels U
A
and U
B
are being used. In this mode voltage memory
is based on line-to-line voltages U12 and U23. In case 2LL+U0 mode is used, voltage memory is based
on calculated phase-to-neutral voltages.
Pick-up characteristics
VMEM activation voltage and measured current condition 3I>
AQ-T257
Instruction manual
Version: 2.00
© Arcteq Relays Ltd
180
