ABB REL670 2.2 IEC - Page 280

SEMOD154680-267 v2
A
B
Z<
Z<
Z<
C
T
IC
IA
IB
-IB
en05000224.vsd
DOCUMENT11524-IMG869 V1 EN-US
Figure 143: 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 will be
ZA =ZAT + ·ZTF
IA + IC
IA
DOCUMENT11524-IMG3509 V3 EN-US
(Equation 201)
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 202)
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
274 Line distance protection REL670 2.2 IEC
Application manual