ABB REB670 Series Applications Manual page 144

Section 6
Differential protection
Main CT
2000/1A or 2000/5A
or 2000/2A
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
calculations for end-connection.
Typical series-connection with ASCT is shown in Figure 85.
Main CT
2000/1A
or 2000/5A
or 2000/2A
Other
relays
Other
relays
IEC06000129 V1 EN-US
Figure 85: Series-connection with ASCT connected to CT3 input
Refer to Section
calculation for series-connection.
138
IL1
L1
IL2
L2
Other
relays
IL3
L3
N
IN
"SLCE 8/ASCT characteristics for end-connection"
L1 L2 L3 N
IL1 IL2 IL3
IN
"SLCE 8/ASCT characteristics for series-connection"
Auxiliary Summation CT
type SLCE 8;
1/1A or 5/1A or 2/1A
I
P1
SUMM
N1
S1
P2
P3
N4
N2
P4
P5
N3
S2
P6
Auxiliary Summation CT
type SLCE 8; 1/1 or 5/1A or 2/1A
IL1
I
P1
SUMM
N1
S1
P2
P3
N4
N2
IL3
P4
P5
N3
IN
S2
P6
1MRK 505 370-UEN D
REB 670 with 1A CTs
en06000128.vsd
for detailed ASCT current
REB 670 with 1A CTs
en06000129.vsd
for detailed ASCT current
Busbar protection REB670
Application manual