ABB REL670 2.2 IEC - Tapped Line Application

8.4.2.8 Tapped line application
SEMOD154453-265 v2
SEMOD154453-267 v4
C
B
BC
IEC09000160-3-en.vsd
A
IEC09000160 V3 EN-US
Figure 128: 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
A C
A AT TF
A
I I
Z Z Z
I
+
= + ×
EQUATION2302 V1 EN-US (Equation 166)
2
A C
C Trf CT TF
C
I I
U2
Z Z Z Z
I U1
+
= + + × ×
æ ö
æ ö
ç ÷
ç ÷
è ø
è ø
IECEQUATION1750 V1 EN-US (Equation 167)
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).
Section 8 1MRK 506 369-UEN B
Impedance protection
248 Line distance protection REL670 2.2 IEC
Application manual