ABB RELION RET670 - Page 293

~
HV Substation
ZMH PDIS
21 Z<
Y
Y
@
Generator CB
Auxiliary
Transformer
Step-up
Transformer
Excitation
Transformer
HV CB
F
ie
ld
C
B
CT: 4000/5
VT: 13,5kV/110V
70MVA
13,2kV
3062A
65MVA
123/13kV
x
t
=10%
REG670
IEC10000102 V1 EN-US
Figure 135: Application example for generator under-impedance function
The first under-impedance protection zone shall cover 100% of the step-up transformer
impedance with a time delay of 1.0s.
1MRK 504 163-UUS A Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI 287
Application manual