Tapped Line Application - ABB RELION 670 SERIES Applications Manual

1MRK 506 369-UUS -
8.3.2.7
Line distance protection REL670 2.2 ANSI
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

ANSI05000224 V2 EN
Figure 120: 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 V3 EN
A
C
·Z
TF
Section 8
Impedance protection
B
BC
ANSI05000224-2-en.vsd
"Fault infeed
(Equation 127)
239