ABB RELION 670 Series Applications Manual page 113

1MRK 505 337-UUS A
6.1.3.10 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 48.
Feeder
Protection
ANSI06000138 V1 EN-US
Figure 48: Typical CT locations in a feeder bay
where:
A
B
C
1
In figure 48, /A where two CTs are available in a feeder bay the end fault protection is not an issue.
The busbar and feeder protection zones overlap across feeder circuit breaker and all faults
between these two CTs will be instantly detected and tripped by both protection schemes. As a
consequence of such fault both busbar and feeder will be disconnected from the power system.
In figure 48/B where one CT is available on the line side of the feeder circuit breaker the primary
fault between CT and CB will cause certain problems. Typically such fault will be detected and
tripped by busbar protection. However to completely clear such fault the remote feeder end CB
must be tripped as well. It shall be noted that for the feeder protection such fault will be either a
reverse fault (that is, distance protection used for feeder protection) or external fault (that is, line/
transformer differential protection used for feeder protection).
In figure 48/C where one CT is available on the bus side of the feeder circuit breaker the primary
fault between CT and CB will cause problem as well. Typically such fault will be detected and
tripped by feeder protection. However, to completely clear such fault the associated busbar
section must be tripped as well. It shall be noted that the busbar differential protection will
classify such fault as external and without any additional measures the busbar protection will
remain stable.
For better understanding end fault protection applications within busbar protection, the figure
is used.
Application manual
Busbar
BI1
Protection
152
BI1
Feeder
A
Protection
= two CTs are available one on each side of the feeder circuit breaker
= one CT is available on the line side of the feeder circuit breaker
= one CT is available on the bus side of the feeder circuit breaker
= End fault region
primary faults between main CT and CB in a feeder bay.
Busbar
Protection
152
Feeder
Protection
BI1
1
B
Differential protection
Busbar
Protection
BI1
152
1
C
en06000138_ansi.vsd
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