ABB RELION 670 Series Applications Manual page 213

1MRK 504 152-UEN B
A
Z<
IEC09000251 V1 EN-US
Figure 114: 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 115.
I
A
B
IEC09000252 V1 EN-US
Figure 115: Equivalent zero sequence impedance circuit for the double-circuit line that
Here the equivalent zero-sequence impedance is equal to Z
Z ) and Z
0m
=
Z
E
EQUATION2002 V4 EN-US
The influence on the distance measurement will be a considerable overreach, which must be
considered when calculating the settings.
All expressions below are proposed for practical use. They assume the value of zero sequence,
mutual resistance R
X . Calculate the equivalent X
0m
and equation
underreaching zone.
=
R
0
E
DOCUMENT11520-IMG3502 V2 EN-US
=
X
0 E
DOCUMENT11520-IMG3503 V2 EN-US
Application manual
B
Z
0m
Z<
IEC09000251_1_en.vsd
-
Z Z
0 0m
0
Z
0m
-
Z
Z
0
0m
IEC09000252_1_en.vsd
operates with one circuit disconnected and earthed at both ends
which is equal to equation 131.
0m
2 2
-
Z Z
0 om
Z
0
equals to zero. They consider only the zero sequence, mutual reactance
0m
133 for each particular line section and use them for calculating the reach for the
2
 
X
0 m
⋅  1 + 
R
0
 
2 2
+
R X
 
0 0
2
 
X
0 m
⋅ 1 −
X  
0
 
2 2
+
R X
 
0 0
I
0
C
and R zero sequence parameters according to equation
0E 0E
Impedance protection
-Z m in series with parallel of (Z
0 0
Section 7
-
0
(Equation 131)
132
(Equation 132)
(Equation 133)
207