1. All used line-to-line or line-to-neutral voltages need to be below the set value for the "VMEM
activation voltage" parameter.
2. At least one phase current must be above the set value for the "Measured current condition
3I>" parameter. This setting limit is optional.
Figure. 5.4.32 - 175. Distance protection characteristics and directional overcurrent.
Voltage memory activates when the above-mentioned criteria are met. Voltage memory uses
the "VMEM activation voltage" parameter as voltage amplitude even when the actual measured voltage
has decreased below it or close to zero. The angle used by this function is the one captured
the moment before the fault occurred and voltage memory was activated. When voltage memory is
activated, the output "Voltage memory on" signal is activated. This signal can be found in the device's I/
O matrix.
While voltage memory is active, voltages are absent and therefore angle measurement is not possible.
Healthy state angles (before a fault) are used during a fault. This is why a drift between the assumed
voltage angle and the actual measured phase current angle takes place. While voltage memory is
used, the angle of phase currents drifts approximately one degree for each passing second (see the
graph below).
A
AQ
Q-M257
-M257
Instruction manual
Version: 2.07
© Arcteq Relays Ltd
IM00021
337
Содержание AQ-M257
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Страница 449: ...Figure 7 3 221 Example block scheme A AQ Q M257 M257 Instruction manual Version 2 07 Arcteq Relays Ltd IM00021 447...
Страница 470: ...Figure 8 14 243 Device installation A AQ Q M257 M257 Instruction manual Version 2 07 468 Arcteq Relays Ltd IM00021...