en04000283.vsd
ZA
21 10
ZB
21 10
BS
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
49 for a two-zone differential
protection application.
en06000137.vsd
QA1
Zone A
Zone B
ZI
ACTIVE
BOM
BIM
REB 670
Bus coupler
EXTSTART
ALARM
Indication that
Zone interconnection
is active
&
B
C
C
B
c
l
o
s
i
n
g
s
w
i
t
c
h
QB1
QB2
t
tOFF=1.0s
1
IEC06000137 V1 EN-US
Figure 49: Configuration logic for bus coupler without main CTs
6.1.3.7 End fault protection
SEMOD127750-31 v4
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
primary
faults between main CT and CB in a feeder bay.
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.
1MRK 505 370-UEN D Section 6
Differential protection
Busbar protection REB670 105
Application manual
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