Z0m
A
B
21
21
en05000222_ansi.vsd
CLOSED
CLOSED
OPEN
OPEN
ANSI05000222 V1 EN-US
Figure 74:
The parallel line is out of service and grounded
When the parallel line is out of service and grounded 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 75:
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 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 42)
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.
Section 8
1MRK 504 163-UUS A
Impedance protection
200
Transformer protection RET670 2.2 ANSI
Application manual
Summary of Contents for RELION RET670
Page 1: ...RELION 670 SERIES Transformer protection RET670 Version 2 2 ANSI Application manual ...
Page 2: ......
Page 48: ...42 ...
Page 64: ...58 ...
Page 74: ...68 ...
Page 104: ...98 ...
Page 194: ...188 ...
Page 518: ...512 ...
Page 618: ...612 ...
Page 648: ...642 ...
Page 666: ...660 ...
Page 672: ...666 ...
Page 682: ...676 ...
Page 844: ...838 ...
Page 868: ...862 ...
Page 956: ...950 ...
Page 964: ...958 ...
Page 1004: ...998 ...
Page 1014: ...1008 ...
Page 1015: ...1009 ...