ABB REL670 2.2 IEC, Applications Manual

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en05000220.vsd
R
Zm
ARGLd
ARGLd
ARGLd
ARGLd
RLdFw RLdRv
ZL
IEC05000220 V1 EN-US
Figure 187: Characteristic for zone measurement for a long line
[6]
8.13.2.6 Parallel line application with mutual coupling
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General
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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 zero sequence measurement due to the
mutual coupling between the parallel lines. The lines need not be of the same
voltage in order to have mutual coupling, and some coupling exists even for lines
that are separated by 100 meters or more. The mutual coupling 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.
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.
The different network configuration classes are:
1. Parallel line with common positive and zero sequence network
2. Parallel circuits with common positive but separated zero sequence network
3. Parallel circuits with positive and zero sequence sources separated.
[6] RLdRv=RLdRvFactor*RLdFw.
1MRK 506 369-UEN B
Section 8
Impedance protection
Line distance protection REL670 2.2 IEC 365
Application manual