Other
relays
IA
IB
IC
en06000129_ansi.vsd
IC
Auxiliary Summation CT
type SLCE 8; 1/1 or 5/1A or 2/1A
N4
S1
S
2
A103
X401
5
6
REB 670 with 1A CTs
C
B
A
N
IA
IN
IN
Main CT
2000/1A
or 2000/5A
or 2000/2A
I
SUMM
Other
relays
P1
N1
P2
P3
N2
P4
P5
N3
P6
ANSI06000129 V1 EN-US
Figure 86:
Series-connection with ASCT connected to CT3 input
Refer to Section
"SLCE 8/ASCT characteristics for series-connection"
for detailed
ASCT current calculation for series-connection.
6.1.6.4
Main CT ratio mismatch correction
M12138-3 v2
As stated before, three types of ASCTs for REB670 are available. The first type shall
be used for main CTs with 1A rated secondary current. The second type shall be used
for main CTs with 5A rated secondary current. The third type shall be used with 2A
main CTs. However REB670 with 1A CT inputs is always used. Therefore main CT
ratio shall always be set in such a way that the primary current is entered as for the
main CT, but secondary current is always entered as 1A (that is, 3000/5 main CT will
be entered as 3000/1 CT in REB670).
6.1.6.5
Primary pick-up levels for summation type differential protection
M12139-3 v4
The minimal differential operating current level is entered directly in primary amperes.
However, as stated previously, in case of the summated differential protection the
primary fault sensitivity varies depending on the type of fault and involved phase(s).
The entered value, for the minimal differential operating current level, will exactly
correspond to the REB670 pickup value in the event of a 3-phase internal fault. For all
1MRK 505 370-UUS A
Section 6
Differential protection
Busbar protection REB670 2.2 ANSI
169
Application manual
Summary of Contents for RELION REB670
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