en05000220_ansi.vsd
R
Zm
LdAngle
LdAngle
LdAngle
LdAngle
RLdFwd
RLdRev
ZL
ANSI05000220 V1 EN-US
Figure 71:
Characteristic for zone measurement for long line with load
encroachment activated
8.1.2.6
Parallel line application with mutual coupling
SEMOD168232-149 v2
General
SEMOD168232-151 v2
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.
From an application point of view there exists three types of network configurations
(classes) that must be considered when making the settings for the protection function.
Those are:
1MRK 504 163-UUS A
Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI
195
Application manual
Содержание RELION RET670
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