ABB REB670 Series - Page 144

L1
L2
L3
N
IL1
IL2
IL3
IN
Other
relays
Auxiliary Summation CT
type SLCE 8;
1/1A or 5/1A or 2/1A
N4
S1
S2
en06000128.vsd
Main CT
2000/1A or 2000/5A
or 2000/2A
A I 0 3
X 4 0 1
5
6
REB 670 with 1A CTs
P1
N1
P2
P3
N2
P4
P5
N3
P6
I
SUMM
IEC06000128 V1 EN-US
Figure 84: End-connection with ASCT connected to CT3 input
It is important to notice that even in the case of 5A or 2A main CTs, secondary current of the
summation CTs shall be connected to the IED with 1A CT inputs (as shown in Figure 84). The
reason for this is that the rated secondary current of ASCT is always 1A irrespective of the
rated secondary current of the main CT.
Refer to section
"SLCE 8/ASCT characteristics for end-connection" for detailed ASCT current
calculations for end-connection.
Typical series-connection with ASCT is shown in Figure
85.
Other
relays
IL1 IL2 IL3
en06000129.vsd
IL3
Auxiliary Summation CT
type SLCE 8; 1/1 or 5/1A or 2/1A
N4
S1
S2
A 1
0 3
X 4 0 1
5
6
REB 670 with 1A CTs
L3L2L1 N
IL1
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
IEC06000129 V1 EN-US
Figure 85: 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.
Section 6 1MRK 505 370-UEN D
Differential protection
138 Busbar protection REB670
Application manual