R
Z1
ArgLd
RLdFw
IEC09000248-3-en.vsdx
X
RLdRv
[1]
IEC09000248 V3 EN-US
Figure 149: Load encroachment phenomena and shaped load encroachment
characteristic defined in Phase selection and load encroachment
function (FRPSPDIS)
8.9.2.4 Short line application
GUID-504F03E4-37CA-4CCF-9DBB-82B8F1C3B3DD v1
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 26.
Table 26: Typical length 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
149.
For very short line applications, the underreaching zone 1 can not be used due to
the voltage drop distribution throughout the line will be too low causing risk for
overreaching.
Load encroachment is normally no problems for short line applications.
8.9.2.5 Long transmission line application
GUID-40F06841-F192-4159-87BA-7BC7E4B014AA v1
For long transmission lines, the margin to the load impedance, that is, to avoid load
encroachment, will normally be a major concern. It is well known that it is difficult
Section 8 1MRK 506 369-UEN B
Impedance protection
296 Line distance protection REL670 2.2 IEC
Application manual
To Next Page
Loading...
