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

1MRK 504 152-UEN B
What can be recognized as long lines with respect to the performance of distance protection
can generally be described as in table 24, long lines have Source impedance ratio (SIR's) less
than 0.5.
Table 24: Definition of long and very long lines
Line category
Long lines
Very long lines
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 111.
ARGLd
ARGLd
IEC05000220 V1 EN-US
Figure 111: Characteristic for zone measurement for a long line
7.3.2.6

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 in order to experience mutual coupling,
and some coupling exists even for lines that are separated by 100 meters or more. The mutual
coupling does influence the zero sequence impedance to the fault point but it does not
normally cause voltage inversion.
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 a
practice to neglect them.
Application manual
Un
110 kV
77 km - 99 km
> 99 km
Zm
ZL
ARGLd
ARGLd
RLdRv RLdFw
en05000220.vsd
Un
500 kV
350 km - 450 km
> 450 km
R
Section 7
Impedance protection
M17048-417 v2
M17048-567 v3
203