ABB RET670 - Page 180

A
B
C
IEC09000255_1_en.vsd
I
0
I
0
Z
0m
Z
0
-
Z
0m
Z
0m
Z
0
-
IEC09000255 V1 EN
Figure 56: Equivalent zero-sequence impedance circuit for a double-circuit line
with one circuit disconnected and not grounded
The reduction of the reach is equal to equation 69.
( )
( )
( )
2
1 0
0
1 0
0
1 0
1
2
3
1
1
2 3
2
3
E f
m
U
f
f
Z Z R
Z
K
Z Z Z R
Z Z R
× × + +
= = -
× × + +
× × + +
EQUATION1284 V1 EN (Equation 69)
This means that the reach is reduced in reactive and resistive directions. If the real and
imaginary components of the constant A are equal to equation 70 and equation 71.
Re( ) 0 (2 1 0 3 ) 0 ( 0 2 1)A R R R Rf X X X= × × + + × - × + ×
EQUATION1285 V1 EN (Equation 70)
0 1 0 1 0 1 0
Im( ) (2 3 ) (2 )A X R R R R X X= × × + + × + × × +
EQUATION1286 V1 EN (Equation 71)
The real component of the KU factor is equal to equation 72.
( )
( )
( ) ( )
2
0
2 2
Re
Re 1
Re Im
m
U
A X
K
A A
×
= +
+
é ù é ù
ë û ë û
EQUATION1287 V2 EN
(Equation 72)
The imaginary component of the same factor is equal to equation 73.
( )
( )
( ) ( )
2
0
2 2
Im
Im
Re Im
m
U
A X
K
A A
×
=
+
é ù é ù
ë û ë û
EQUATION1288 V2 EN (Equation 73)
Section 3 1MRK504116-UUS C
IED application
174
Application manual