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2
2
0
0
om
E
Z
Z
Z
Z
-
=
EQUATION2002 V4 EN-US
(Equation 215)
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
for each particular line section and use
them for calculating the reach for the underreaching zone.
R
R
X
R
X
E
m
0
0
0
2
0
2
0
2
1
=
⋅
+
+
DOCUMENT11520-IMG3502 V2 EN-US
(Equation 216)
X
X
X
R
X
E
m
0
0
0
2
0
2
0
2
1
=
⋅
−
+
DOCUMENT11520-IMG3503 V2 EN-US
(Equation 217)
Parallel line out of service and not grounded
GUID-0458F8AF-BDAC-4F07-B289-15B172FB39D9 v1
Z0m
A
OPEN
21
21
en05000223_ansi.vsd
CLOSED
OPEN
CLOSED
B
ANSI05000223 V1 EN-US
Figure 158:
Parallel line is out of service and not grounded.
When the parallel line is out of service and not grounded, the zero sequence on that
line can only flow through the line admittance to the ground. The line admittance is
Section 8
1MRK 504 163-UUS A
Impedance protection
334
Transformer protection RET670 2.2 ANSI
Application manual
Summary of Contents for RELION RET670
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