ABB Relion 670 Series Technical Reference Manual page 175

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