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-ground 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
113.
en05000220_ansi.vsd
R
Zm
LdAngle
LdAngle
LdAngle
LdAngle
RLdFwdRLdRev
ZL
ANSI05000220 V1 EN
Figure 113: Characteristic for zone measurement for a long line
8.3.2.6 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.
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 231
Application manual
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