Z0m
A B
21
21
en05000222_ansi.vsd
CLOSED
CLOSED
OPEN OPEN
ANSI05000222 V1 EN
Figure 192: The parallel line is out of service and grounded
When the parallel line is out of service and grounded at both line ends on the bus bar side
of the line CTs so that zero sequence current can flow on the parallel line, the equivalent
zero sequence circuit of the parallel lines will be according to figure
117.
A
B
C
IEC09000252_1_en.vsd
I
0
I
0
Z
0m
Z
0
-
Z
0m
Z
0
-
Z
0m
IEC09000252 V1 EN
Figure 193: Equivalent zero sequence impedance circuit for the double-circuit line
that operates with one circuit disconnected and grounded at both ends
Here the equivalent zero-sequence impedance is equal to Z
0
-Z
0
m in parallel with (Z
0
-
Z
0m
)/Z
0
-Z
0m
+Z
0m
which is equal to equation 119.
EQUATION2002 V4 EN
(Equation 348)
The influence on the distance measurement will be a considerable overreach, which must
be considered when calculating the settings. It is recommended to use a separate setting
group for this operation condition since it will reduce the reach considerably when the line
is in operation.
All expressions below are proposed for practical use. They assume the value of zero
sequence, mutual resistance R
0m
equals to zero. They consider only the zero sequence,
mutual reactance X
0m
. Calculate the equivalent X
0E
and R
0E
zero sequence parameters
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 395
Application manual
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