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The settings of the parameters for load encroachment are done in the Phase selection
with load enchroachment, quadrilateral characteristic (FDPSPDIS,21).
R
X
Zm
RldRev
R
Zm
RLdFwd
ZL
ANSI05000495_2_en.vsd
Load impedance area in
forward direction
LdAngle
LdAngle
LdAngle
LdAngle
ANSI05000495 V2 EN-US
Figure 140:
Load encroachment phenomena and shaped load encroachment
characteristic
8.5.2.5
Short line application
SEMOD154680-105 v2
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
Table 28:
Definition of short and very short line
Line category
Vn
Vn
110 kV
500 kV
Very short line
Short line
0.75-3.5 miles
3-15 miles
4-7 miles
15-30 miles
The possibility in IED 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-ground fault together with load encroachment algorithm improves the
possibility to detect high resistive faults without conflict with the load impedance, see
figure
.
For very short line applications the underreaching zone 1 can not be used due to that
the voltage drop distribution through out the line will be too low causing risk for
overreaching.
Section 8
1MRK 504 163-UUS A
Impedance protection
296
Transformer protection RET670 2.2 ANSI
Application manual
Содержание RELION RET670
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