while the fictive voltage is in use. When the voltage is below
Min operate voltage
and hysteresis and the fictive voltage is unusable, the fault direction cannot be
determined. The fictive voltage can be unusable for two reasons:
• The fictive voltage is discarded after
Voltage Mem time
• The phase angle cannot be reliably measured before the fault situation.
DPHxPDOC can be forced to the non-directional operation with the NON_DIR
input. When the NON_DIR input is active, DPHxPDOC operates as a non-directional
overcurrent protection, regardless of the
Directional mode
setting.
Figure 207: Operating zones at minimum magnitude levels
The DIRECTION output indicates on which operating sector the current is
measured. The value combines phase-specific directions which are available in
monitored data as DIR_A, DIR_B and DIR_C.
Level detector
The measured phase currents are compared phasewise to the set
Start value
. If the
measured value exceeds the set
Start value
, the level detector reports the exceeding
of the value to the phase selection logic. If the ENA_MULT input is active, the
Start
value
setting is multiplied by the
Start value Mult
setting.
The protection relay does not accept the
Start value
or
Start value Mult
setting if the product of these settings exceeds the
Start value
setting
range.
Protection functions 1MRS759142 F
348 REX640
Technical Manual
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