ABB Relion 670 series, Applications Manual

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this corresponds to the per-phase, or positive-sequence, impedance. For a phase-to-earth
fault, it corresponds to the per-loop impedance, including the earth return impedance.
R
X
RLdFw
RLdRv
ArgLd
90%
10%
10%
ARGLd
Possible
load
ARGLd
ARGLd
R
X
RLdFw
RLdRv
X
L
d
X
L
d
ARGLd
ARGLd
ARGLd
ARGLd
IEC12000176-2-en.vsd
IEC12000176 V2 EN-US
Figure 197: Load impedance limitation with load encroachment
During the initial current change for phase-to-phase and for phase-to-earth faults, operation
may be allowed also when the apparent impedance of the load encroachment element is
located in the load area. This improves the dependability for fault at the remote end of the line
during high load. Although it is not associated to any standard event, there is one potentially
hazardous situation that should be considered. Should one phase of a parallel circuit open a
single pole, even though there is no fault, and the load current of that phase increase, there is
actually no way of distinguish this from a real fault with similar characteristics. Should this
accidental event be given precaution, the phase-to-earth reach (RFPE) of all instantaneous
zones has to be set below the emergency load for the pole-open situation. Again, this is only
for the application where there is a risk that one breaker pole would open without a preceding
fault. If this never happens, for example when there is no parallel circuit, there is no need to
change any phase-to-earth reach according to the pole-open scenario.
7.12.3.9 Other settings
GUID-9D65B411-6FE2-433B-AE6C-C6DD716D1181 v5
IMinOpPE and IMinOpPP
The ability for a specific loop and zone to issue a start or a trip is inhibited if the magnitude of
the input current for this loop falls below the threshold value defined by these settings. The
output of a phase-to-earth loop Ln is blocked if ILn < IminOpPE(Zx). In is the RMS value of the
fundamental current in phase n.
The output of a phase-to-phase loop LmLn is blocked if ILmLn <
IMinOpPP(Zx). ILmLn is the
RMS value of the vector difference between phase currents Lm and Ln.
Both current limits
IMinOpPE and IMinOpPP are automatically reduced to 75% of regular set
values if the zone is set to operate in reverse direction, that is,
OperationDir is set to Reverse.
OpModePPZx and OpModePEZx
These settings, two per zone (x=1,2..5&RV), with options {Off, Quadrilateral, Mho, Offset}, are
used to set the operation and characteristic for phase-to-earth and phase-to-phase faults,
respectively.
For example, in one zone it is possible to choose Mho characteristic for the three Ph-Ph
measuring loops and Quadrilateral characteristic for the three Ph-E measuring loops.
DirModeZx
1MRK 505 343-UEN B Section 7
Impedance protection
321
Application manual