Ensure that the underreaching zones from both line ends will overlap a sufficient amount
(at least 10%) in the middle of the protected circuit.
8.13.2.7 Tapped line application
C
A
B
BC
ANSI05000224-2-en.vsd
ANSI05000224 V2 EN
Figure 196: Example of tapped line with Auto transformer
This application gives rise to a similar problem that was highlighted in section Fault infeed
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:
DOCUMENT11524-IMG3509 V3 EN
(Equation 356)
A C
2
C Trf CT TB
C
I I V2
Z Z (Z Z ) ( )
V1
I
+
= + + × ×
EQUATION1714 V1 EN (Equation 357)
Section 8 1MRK 506 369-UUS -
Impedance protection
398 Line distance protection REL670 2.2 ANSI
Application manual
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