ABB Relion 670 Series Applications Manual page 112

Section 6
Differential protection
With GIS or live tank circuit breakers, owing to high cost of HV CT installations, sometimes no current
transformers are available in bus-section or bus-coupler bay. This is the third solution shown in Figure
ANSI04000283 V1 EN-US
Figure 49:
In such case two separate zones can be maintained only while bus coupler breaker is open. As soon as
bus coupler breaker is going to be closed the zone interconnection feature must be activated and
complete busbars will be automatically protected with just one differential zone.
Since there are no current transformer in the bus coupler bay, there is no need to allocate internal bay
function block for the bus coupler bay. However some additional configuration logic is required to obtain
automatic zone interconnection activation when bus coupler breaker shall be closed. Example of such
logic, is shown in Figure
289
189
Bus coupler
ANSI06000137 V1 EN-US
Figure 50:
106
ZA
1 2 10
Example of station without main CTs in the bus-section bay
50 for a two-zone differential protection application.
Zone A
Zone B
REB 670
BIM
0-tOFF
52b
152
Configuration logic for bus coupler without main CTs
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BS
ZB
1 2
ZI
AND NOT
EXTSTART
1MRK 505 370-UUS Rev. K
10
en04000283_ansi.vsd
BOM
ACTIVE
ALARM
Indication that
Zone interconnection
is active
en06000137_ansi.vsd
Busbar protection REB670
Application manual
49