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1MRK 505 370-UEN D
IEC04000283 V1 EN-US
Figure 48: Example of station without main CTs in the bus-section bay
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
protection application.
QB1
QB2
QA1
Bus coupler
IEC06000137 V1 EN-US
Figure 49: Configuration logic for bus coupler without main CTs
6.1.3.7
End fault protection
When Live tank CBs or GIS are involved, there is a physical separation between the CT and the
CB. End Fault Protection is related to
Therefore, it is directly related to the position of the main CT in feeder bay. Three CT positions
in feeder bays are typically used in power systems around the world, as shown in Figure 50.
Busbar protection REB670
Application manual
ZA
1
2
10
Zone A
Zone B
REB 670
BIM
tOFF=1.0s
BS
1
t
&
1
primary faults between main CT and CB in a feeder bay.
Differential protection
ZB
2
10
en04000283.vsd
49
for a two-zone differential
BOM
ZI
EXTSTART
ACTIVE
ALARM
Indication that
Zone interconnection
is active
en06000137.vsd
Section 6
SEMOD127750-31 v4
105
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