Parallel Line Application With Mutual Coupling - ABB RELION 670 Series Applications Manual

1MRK 504 152-UEN B
Definition of long lines with respect to the performance of distance protection can generally
be described as in table 22, long lines have SIR's less than 0.5.
Table 22:
Line category
Long lines
Very long lines
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-
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), as shown in figure 58.
ARGLd
ARGLd
IEC05000220 V1 EN-US
Figure 58: Characteristic for zone measurement for long line with load encroachment
7.1.2.6

Parallel line application with mutual coupling

General
Introduction of parallel lines in the network is increasing due to difficulties to get necessary
area for new lines.
Parallel lines introduce an error in the measurement due to the mutual coupling between the
parallel lines. The lines need not be of the same voltage to experience mutual coupling, and
some coupling exists even for lines that are separated by 100 meters or more. The reason to
the introduced error in measuring due to mutual coupling is the zero sequence voltage
inversion that occurs.
It can be shown from analytical calculations of line impedances that the mutual impedances
for positive and negative sequence are very small (< 1-2%) of the self impedance and it is
practice to neglect them.
Application manual
Definition of long lines
Un
110 kV
77 km - 99 km
> 99 km
Zm
ZL
RLdRv RLdFw
en05000220.vsd
activated
Un
500 kV
350 km - 450 km
> 450 km
ARGLd
R
ARGLd
Section 7
Impedance protection
SEMOD168232-149 v2
SEMOD168232-151 v2
149