Nevertheless, always set RLdFw, RLdRv
[5]
and ArgLd according to the expected
maximum load since these settings are used internally in the function as reference
points to improve the performance of the phase selection.
R
Z1
ArgLd
RLdFw
IEC09000248-3-en.vsdx
X
RLdRv
[1]
IEC09000248 V3 EN
Figure 97: Load encroachment phenomena and shaped load encroachment
characteristic
8.3.2.4 Short line application
In short line applications, the major concern is to get sufficient fault resistance
coverage. Load encroachment is not so common. The line length that can be
recognized as a short line is not a fixed length; it depends on system parameters such
as voltage and source impedance, see table 25.
Table 27: Definition of short and very short line
Line category
Un Un
110 kV 500 kV
Very short line 1.1-5.5 km 5-25 km
Short line 5.5-11 km 25-50 km
The IED's ability to set resistive and reactive reach independent for positive and zero
sequence fault loops and individual fault resistance settings for phase-to-phase and
phase-to-earth fault together with load encroachment algorithm improves the
possibility to detect high resistive faults without conflict with the load impedance, see
figure
97.
For very short line applications, the underreaching zone 1 cannot be used due to the
voltage drop distribution throughout the line will be too low causing risk for
overreaching.
Load encroachment is normally no problem for short line applications.
[5] RLdRv=RLdRvFactor*RLdFw.
Section 8 1MRK 502 071-UEN -
Impedance protection
218 Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
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