ABB REL670 2.2 IEC - Page 309

Parallel line out of service and not earthed
GUID-0458F8AF-BDAC-4F07-B289-15B172FB39D9 v1
Z
0m
A B
Z< Z<
IEC09000254_1_en.vsd
IEC09000254 V1 EN-US
Figure 154: Parallel line is out of service and not earthed.
When the parallel line is out of service and not earthed, the zero sequence on that
line can only flow through the line admittance to the earth. The line admittance is
high which limits the zero sequence current on the parallel line to very low values.
In practice, the equivalent zero sequence impedance circuit for faults at the remote
bus bar can be simplified to the circuit shown in figure
154
The line zero sequence mutual impedance does not influence the measurement of
the distance protection in a faulty circuit.
A
B
C
IEC09000255_1_en.vsd
I
0
I
0
Z
0m
Z
0
-
Z
0m
Z
0m
Z
0
-
IEC09000255 V1 EN-US
Figure 155: Equivalent zero sequence impedance circuit for a double-circuit
line with one circuit disconnected and not earthed.
1MRK 506 369-UEN B Section 8
Impedance protection
Line distance protection REL670 2.2 IEC 303
Application manual