![background image](http://html1.mh-extra.com/html/abb/relion-670-series/relion-670-series_applications-manual_3052129159.webp)
Z0m
A
B
Z<
Z<
en05000222.vsd
DOCUMENT11520-IMG867 V1 EN-US
Figure 76: The parallel line is out of service and earthed
When the parallel line is out of service and earthed at both ends on the bus bar side of the line
CT 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
Z
Z
0
m0
Z
Z
0
m0
Zm0
A
B
C
99000039.vsd
I
0
I
0
DOCUMENT11520-IMG7100 V1 EN-US
Figure 77: 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 Z0-Z0m in parallel with (Z0-
Z0m)/Z0-Z0m+Z0m which is equal to equation
.
2
2
0
0
om
E
Z
Z
Z
Z
-
=
EQUATION2002 V4 EN-US
(Equation 55)
The influence on the distance measurement can 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 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
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 56)
X
X
X
R
X
E
m
0
0
0
2
0
2
0
2
1
=
⋅
−
+
DOCUMENT11520-IMG3503 V2 EN-US
(Equation 57)
1MRK 505 343-UEN B
Section 7
Impedance protection
153
Application manual
Summary of Contents for Relion 670 series
Page 1: ...RELION 670 SERIES Line differential protection RED670 Version 2 1 IEC Application manual...
Page 2: ......
Page 40: ...34...
Page 64: ...58...
Page 150: ...144...
Page 406: ...400...
Page 472: ...466...
Page 494: ...488...
Page 512: ...506...
Page 524: ...518...
Page 604: ...598...
Page 686: ...680...
Page 718: ...712...
Page 722: ...716...
Page 758: ...752...
Page 759: ...753...