ABB RET670 Applications Manual page 208

Section 3
IED application
202
( )
= +
Re K 1
U
é
Re
ë
EQUATION1287 V2 EN
The imaginary component of the same factor is equal to equation 118.
( )
×
Im A X
( )
=
Im K
U
( )
2
é ù
+
Re A
ë û
EQUATION1288 V2 EN
Ensure that the underreaching zones from both line ends will overlap a sufficient
amount (at least 10%) in the middle of the protected circuit.
Tapped line application
A
I
21
ANSI05000224 V1 EN
Figure 70: Example of tapped line with Auto transformer
( )
×
2
Re A X
m 0
( ) ( )
2 2
ù é ù
+
A Im A
û ë û
2
m 0
( )
2
é ù
Im A
ë û
A
T
I
C
21
C
1MRK504116-UUS C
(Equation 117)
(Equation 118)
B
I
B
21
-I
B
en05000224_ansi.vsd
Application manual