Z
0m
A
B
Z<
Z<
IEC13000256-1-en.vsd
x
Ph-G
IEC13000256 V1 EN-US
Figure 130:
Parallel line is out of service and not earthed
0
1
1
1
1
1
3
N
Z
x Z
K
Z
Z
Z
+
= ×
+
-
×
IECEQUATION14012 V1 EN-US
(Equation 171)
Case 3: Both lines in service
Z
0m
A
B
Z<
Z<
IEC13000257-1-en.vsd
x
Ph-G
IEC13000257 V1 EN-US
Figure 131:
Class 1, parallel line in service
GUID-354B9143-D19E-4835-BCEA-737D7C5E02AA V1 EN-US
(Equation 172)
Some observations from above equations for case 1, 2, and 3
GUID-6B411616-EB82-4447-BC2D-375D042BE110 v1
In case 1, the lowest impedance is measured, that is, the highest reach occurs due to
the parallel connection of the zero-sequence systems of both lines.
In case 3, the highest impedance is measured, which corresponds to the shortest
reach.
The mutual impedance will influence the distance measurement of ground faults
and cause either an extension or a reduction of the reach relative to the set reach.
1MRK 506 369-UEN B
Section 8
Impedance protection
Line distance protection REL670 2.2 IEC
253
Application manual
Содержание REL670 2.2 IEC
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