ABB REL650 Applications Manual page 129

1MRK 506 334-UUS A
Application manual
A
OPEN
CLOSED
21
ANSI05000222 V1 EN
Figure 56: The parallel line is out of service and grounded
When the parallel line is out of service and grounded 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 57.
-
Z Z
I 0 0m
A
0
-
Z Z
0
B 0m
IEC09000252 V1 EN
Figure 57: Equivalent zero sequence impedance circuit for the double-circuit line
that operates with one circuit disconnected and grounded at both ends
Here the equivalent zero-sequence impedance is equal to Z
(Z -Z ) and Z which is equal to equation 44.
0 0m 0m
2 2
-
Z Z
0 om
=
Z
E
Z
0
EQUATION2002 V3 EN
B
OPEN
Z0m
CLOSED
21
en05000222_ansi.vsd
Z
0m
I
0
C
IEC09000252_1_en.vsd
Section 6
Impedance protection
-Z m in series with parallel of
0 0
(Equation 44)
123