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.
So, for short lines, the load encroachment function could preferably be switched
off. See section
"Load impedance limitation, without load encroachment function".
The settings of the parameters for load encroachment are done in FDPSPDIS
function.
R
Z1
ArgLd
RLdFw
IEC09000248-3-en.vsdx
X
RLdRv
[1]
IEC09000248 V3 EN-US
Figure 110: Load encroachment phenomena and shaped load encroachment
characteristic defined in Phase selection with load encroachment
function FDPSPDIS
8.3.2.4 Short line application
M17048-97 v4
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
19.
Table 19: 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
110.
1MRK 506 369-UEN B Section 8
Impedance protection
Line distance protection REL670 2.2 IEC 215
Application manual
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