ABB REL670 2.2 IEC, Applications Manual

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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 221: 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 (RFPEZx) 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.
8.13.4.10 Parameter setting guidelines
GUID-B28677F4-B909-42C1-B1B7-1C118B26E67D v4
IMinOpPEZx and IMinOpPPZx
The ability for a specific loop and zone to issue start or 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 <
IminOpPEZx . ILn is the RMS value of the fundamental current in phase Ln.
The output of a phase-to-phase loop LmLn is blocked if ILmLn < IMinOpPPZx .
ILmLn is the RMS value of the vector difference between phase currents Lm and
Ln.
Both current limits IMinOpPEZx and IMinOpPPZx are automatically reduced to
75% of regular set values if the zone is set to operate in reverse direction, that is,
OperationDir = Reverse .
Section 8
1MRK 506 369-UEN B
Impedance protection
404 Line distance protection REL670 2.2 IEC
Application manual