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 "Zone reach setting lower than minimum load impedance".
R
Z1
ArgLd
RLdFw
IEC09000248-3-en.vsdx
X
RLdRv
[1]
IEC09000248 V3 EN
Figure 83: Load encroachment phenomena and shaped load encroachment
characteristic
[1]
8.2.2.4 Short line application
In short line applications, the major concern is to get sufficient fault resistance
coverage. Load encroachment is not such a common problem. 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 25: 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.
For very short line applications, the underreaching zone 1 can not be used due to the
fact that the voltage drop distribution throughout the line will be too low causing risk
for overreaching.
[1] RLdRv=RLdRvFactor*RLdFw
1MRK 502 071-UEN - Section 8
Impedance protection
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 193
Application manual
To Next Page
Loading...
