ABB Relion 670 series, Руководство по применению

Страница: 317 / 760

Z
0m
A B
Z< Z<
IEC09000251_1_en.vsd
IEC09000251 V1 EN-US
Figure 191: The parallel line is out of service and earthed
When the parallel line is out of service and earthed 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 192 .
A
B
C
IEC09000252_1_en.vsd
I
0
I
0
Z
0m
Z
0
-
Z
0m
Z
0
-
Z
0m
IEC09000252 V1 EN-US
Figure 192: Equivalent zero sequence impedance circuit for the double-circuit line that
operates with one circuit disconnected and earthed 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 324 .
2 2
0
0
om
E
Z Z
Z
Z
-
=
EQUATION2002 V4 EN-US
(Equation 324)
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 according to equation 325
and equation 326 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 325)
X X
X
R X
E
m
0 0
0
2
0
2
0
2
1 = ⋅ −
+








DOCUMENT11520-IMG3503 V2 EN-US
(Equation 326)
1MRK 505 343-UEN B Section 7
Impedance protection
311
Application manual