ABB RELION RET670 - Tapped Line Application

( )
( )
( ) ( )
2
0
2 2
Im
Im
Re Im
m
U
A X
K
A A
×
=
+
é ù é ù
ë û ë û
EQUATION1288 V2 EN-US (Equation 280)
Ensure that the underreaching zones from both line ends will overlap a sufficient
amount (at least 10%) in the middle of the protected circuit.
8.12.2.7 Tapped line application
GUID-740E8C46-45EE-4CE8-8718-9FAE658E9FCE v1
GUID-7AA566A4-B6E9-41A7-9927-4DAB50BE8D1A v1
C
A
B
BC
ANSI05000224-2-en.vsd
ANSI05000224 V2 EN-US
Figure 183: 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
Section 8 1MRK 504 163-UUS A
Impedance protection
382 Transformer protection RET670 2.2 ANSI
Application manual