Long Transmission Line Application - ABB REG670 Applications Manual

1MRK 502 071-UEN -
8.3.2.5
8.3.2.6
[6] RLdRv=RLdRvFactor*RLdFw.
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual

Long transmission line application

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 to
achieve high sensitivity for phase-to-earth fault at remote line end of long lines when
the line is heavy loaded.
What can be recognized as long lines with respect to the performance of distance
protection can generally be described as in table 26, long lines have Source impedance
ratio (SIR's) less than 0.5.
Table 28: Definition of long and very long lines
Line category Un
110 kV
Long lines 77 km - 99 km
Very long lines > 99 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 at the same time as the security is improved
(risk for unwanted trip due to load encroachment is eliminated), see figure 98.
ARGLd
ARGLd
RLdRv RLdFw
IEC05000220 V1 EN
Figure 98: Characteristic for zone measurement for a long line
[6]
Parallel line application with mutual coupling
Un
500 kV
350 km - 450 km
> 450 km
Zm
ZL
ARGLd
R
ARGLd
en05000220.vsd
Section 8
Impedance protection
219