ABB REL670 2.2 IEC, Applications Manual

Page: 166 / 908

SEMOD168232-268 v2
A B
Z< Z<
Z<
C
T
I
C
I
A
I
B
-I
B
en05000224.vsd
DOCUMENT11524-IMG869 V1 EN-US
Figure 65: Example of tapped line with Auto transformer
This application gives rise to 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 is as follows:
Z
A
=Z
AT
+ ·Z
TF
I
A
+ I
C
I
A
DOCUMENT11524-IMG3509 V3 EN-US
(Equation 42)
Z Z Z
I I
I
Z
U
U
C Trf CT
A C
C
TF
= + +
+
⋅





 ⋅






2
1
2
DOCUMENT11524-IMG3510 V3 EN-US
(Equation 43)
Where:
ZAT and ZCT is the line impedance from the B respective C station to the T point.
IA and IC is fault current from A respective C station for fault between T and B.
U2/U1 Transformation ratio for transformation of impedance at U1 side of the transformer to
the measuring side U2 (it is assumed that current and voltage distance function is
taken from U2 side of the transformer).
Section 8
1MRK 506 369-UEN B
Impedance protection
160 Line distance protection REL670 2.2 IEC
Application manual