Tapped Line Application - ABB REL650 Applications Manual

1MRK 506 334-UUS A
6.1.2.6
Application manual
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 60: Example of tapped line with Auto transformer
This application gives rise to similar problem that was highlighted in section
from remote end" , that is increased measured impedance due to fault current 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 V2 EN
+
I I
A
= + +
Z Z (Z
C Trf CT
I
C
EQUATION1714 V1 EN
A
T
I
C
21
C
·Z
TF
V2
C
× ×
2
Z ) ( )
TB
V1
Section 6
Impedance protection
B
I
B
21
-I
B
en05000224_ansi.vsd
"Fault infeed
(Equation 46)
(Equation 47)
125