ABB Relion REG670, Applications Manual

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C
B
BC
IEC09000160-3-en.vsd
A
IEC09000160 V3 EN
Figure 90: Example of tapped line with Auto transformer
This application gives rise to similar problem that was highlighted in section
"Influence of fault current infeed from remote line 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
Z
A
=Z
AT
+ ·Z
TF
I
A
+ I
C
I
A
DOCUMENT11524-IMG3509 V3 EN
(Equation 56)
Z Z Z
I I
I
Z
U
U
C Trf CT
A C
C
TF
= + +
+
⋅





 ⋅






2
1
2
DOCUMENT11524-IMG3510 V3 EN
(Equation 57)
Where:
Z
AT
and Z
CT
is the line impedance from the A respective C station to the T point.
I
A
and I
C
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).
Z
TF
is the line impedance from the T point to the fault (F).
Z
Trf
Transformer impedance
1MRK 502 071-UEN -
Section 8
Impedance protection
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 201
Application manual