ABB REG670 Applications Manual page 191

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
HV Substation
HV CB
65MVA
Step-up
123/13kV
Transformer
x
Auxiliary
Transformer
Generator CB
Excitation
Transformer
~
CT: 4000/5
IEC10000102 V1 EN
Figure 78: 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.
Calculate the step-up transformer impedance, in primary ohms, from the 13kV side as
follows:
=10%
t
Y
Y
@
VT: 13,5kV/110V
70MVA
13,2kV
3062A
Section 8
Impedance protection
REG670
21 Z<
ZMH PDIS
185