three-phase impedance element have been modified. These zone settings should
be checked to see whether a non-zero TLT_ANG_CONFLICT value has been found
although, internally, the polygon boundary has been closed for existing settings.
Directional lines
The direction of a zone is defined with setting
Directional mode Znx =
"Nondirectional", "Forward" or "Reverse". The directionality of each zone can be
set independently of other zones. For example, zones Z1 and Z2 can be set in the
"Forward" direction and Z3 in the "Reverse" direction. Furthermore, the optionally
supervised earth-fault directional criteria (in low-impedance earthed networks)
given for GFC are checked here together with zone direction criteria fulfilment.
The directionality of a quadrilateral zone is defined with two independent
directional lines. The directional lines can be included into the mho characteristics
to secure the directionality or to transform the non-directional mho characteristic
into a directional one.
The directional lines are adjusted with the
Min phase angle zone and Max phase
angle zone settings, which are common for all the zones. The angles are given in
degrees. The directional lines are polarized with the
Pol quantity zone method. By
default, the polarization method is positive-sequence voltage ("Pos. seq. volt.").
Max phase angle zone
Min phase angle zone
Forward
Max phase angle zone
Min phase angle zone
Reverse
X
R
X
R
Directional mode Znx = Reverse
Directional mode Znx = Forward
Figure 549: Settings that adjust directional lines in case of quadrilateral
characteristics
The calculated direction of the fault or load (if there is no fault present) current
is indicated for each zone with outputs DIRECTION_Z1 - Z5 which may have values
"unknown", "forward", "backward" or "both". It is important to check setting
X1
reverse zone x (or Z1 reverse zone x reactance part) for quadrilateral directional
characteristics (see
and the corresponding phase-to-earth impedance
given in
) so that it does not restrict the negative-reactance reach defined
by settings
Min Ris Gnd/PP Rch Znx and Max phase angle zone.
Memory voltage
The memory voltage is based on the healthy positive-sequence voltage stored
during the network healthy state. This fictive voltage is substituted for the
measured voltage with any impedance measurement element polarization if
the corresponding voltage drops too low (limit is 5% Un). Fictive voltage use
is indicated by the active monitored data output VMEM_USED. The polarized
impedance direction for a corresponding impedance element is frozen after a
fixed 100 ms of fictive voltage use, but the memory function enables impedance
polarization to operate up to a maximum of 300 s. This time can be set with the
1MRS759142 F
Protection functions
REX640
Technical Manual
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