ABB Relion 670 series, Technical Reference Manual, Page: 175 / 1232

PU_37
BLUC
BLOCK
PU_UC
I3P
OR
t
tUC
AND
a<b
a
b
ANSI09000780-1-en.vsd
ANSI09000780 V1 EN
Figure 70: Low current criterion logic diagram
Security logic for differential protection
The configuration for the additional security logic for differential protection is shown
in fig
71 . The function will release tripping of the line differential protection up to the
end of timer tStUpReset .
Phase-phase
current variation
STCV
i
U
LOW
<
I
0
>
27 PU
Pick Up 3IO
PU_UC
OR
Local side start-up
Send signal to
remote side
Zero sequence
current criterion
Low voltage
criterion
Low current
criterion
ANSI10000296-1-en.vsd
I
0
<
REMSTEP
t
tStUpReset
BFI_3P
ANSI10000296 V1 EN
Figure 71: Additional security logic for differential protection. Logic diagram for
start up element.
1MRK505222-UUS C
Section 5
Differential protection
169
Technical reference manual