ABB RET670 Applications Manual page 206

Section 3
IED application
200
2 2
-
Z Z
0 om
=
Z
E
Z
0
EQUATION2002 V4 EN
The influence on the distance measurement can 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 reduces 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 R0m equals to zero. They
consider only the zero-sequence, mutual reactance X0m. Calculate the equivalent X0E
and R0E zero-sequence parameters according to equation
each particular line section and use them for calculating the reach for the
underreaching zone.
æ
2
X
= · +
R R 1 0 m
ç
0 E 0
2 +
R X
è
0
DOCUMENT11520-IMG3502 V1 EN
æ
2
X
= · -
X X 1 0 m
ç
0 E 0
+
2
R X
è
0
DOCUMENT11520-IMG3503 V1 EN
Parallel line out of service and not grounded
A
OPEN
CLOSED
21
ANSI05000223 V1 EN
Figure 68: 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
high which limits the zero sequence current on the parallel line to very low values. In
ö
÷
2
ø
0
ö
÷
2
ø
0
B
OPEN
Z0m
CLOSED
21
en05000223_ansi.vsd
1MRK504116-UUS C
(Equation 111)
112 and equation 113 for
(Equation 112)
(Equation 113)
Application manual