ABB RELION 670 Series Technical Manual page 323

1MRK 502 066-UUS B
The IED has a built in feature which shapes the characteristic according to the characteristic
shown in figure159. The load encroachment algorithm will increase the possibility to detect high
fault resistances, especially for phase-to-ground faults at remote line end. For example, for a given
setting of the load angle
according to
operation due to load encroachment. Separate resistive blinder settings are available in forward
and reverse direction.
The use of the load encroachment feature is essential for long heavily loaded lines, where there
might be a conflict between the necessary emergency load transfer and necessary sensitivity of
the distance protection. The function can also preferably be used on heavy loaded, medium long
lines. For short lines, the major concern is to get sufficient fault resistance coverage. Load
encroachment is not a major problem. See section "".
ANSI05000495 V2 EN-US
Figure 159: Load encroachment phenomena and shaped load encroachment characteristic
[1]
7.8.7.8 Simplified logic schemes
PHSA, PHSB,...PHSCA are internal binary logical signals from the Phase-selection element. They
correspond directly to the six loops of the distance zones and determine which loops should be
released to possibly issue a pickup or a trip.
FWA, FWB,...FWCA and RVA, RVB,...RVCA are the internal binary signals from the Directional
element. An FW signal is activated if the criteria for a forward fault or load is fulfilled for its
particular loop. The equivalent applies to the reverse (RV) signals.
The internal input 'IN present' is activated if the residual current (3I0) exceeds 10% of the
maximum phase current magnitude and at the same time is above 5% of IBase. However, if current
transformer saturation is detected, this criterion is changed to residual voltage (3V0) exceeding
5% of VBase/sqrt(3) instead.
[1] RLdRv=RLdRvFactor*RLdFw
Technical manual
LdAngle , the resistive blinder for the zone measurement can be set
figure159 affording higher fault resistance coverage without risk for unwanted
X
Zm
Load impedance area in
forward direction
R
Zm
ZL
LdAngle
LdAngle
RLdFwd
RldRev
ANSI05000495_2_en.vsd
Section 7
Impedance protection
LdAngle
R
LdAngle
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