ABB RELION RET670 Applications Manual page 279

1MRK 504 163-UUS A
Transformer protection RET670 2.2 ANSI
Application manual
ANSI05000224 V2 EN-US
Figure 131: Example of tapped line with Auto transformer
This application gives rise to similar problem that was highlighted in section
infeed from remote end"
infeed. For example, for faults between the T point and B station the measured
impedance at A and C will be
I + I
A C
Z =Z +
A AT
I
A
DOCUMENT11524-IMG3509 V3 EN-US
+
I I
A
= + +
Z Z (Z
C Trf CT
I
C
EQUATION1714 V1 EN-US
A
, that is increased measured impedance due to fault current
·Z
TF
V2
C
× × 2
Z ) ( )
TB
V1
Impedance protection
B
C
ANSI05000224-2-en.vsd
Section 8
M17048-245 v4
BC
"Fault
(Equation 132)
(Equation 133)
273