ABB RELION REB670, Applications Manual

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en06000138_ansi.vsd
BI1
BI1
Busbar
Protection
Feeder
Protection
BI1
Busbar
Protection
Feeder
Protection
BI1
Busbar
Protection
Feeder
Protection
A B
1
C
1
152 152 152
ANSI06000138 V1 EN-US
Figure 51: Typical CT locations in a feeder bay
where:
A
two CTs are available one on each side of the feeder circuit breaker
B one CT is available on the line side of the feeder circuit breaker
C one CT is available on the bus side of the feeder circuit breaker
1 End fault region
In Figure 51 /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 51 /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 51 /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
52 is provided.
Section 6
1MRK 505 370-UUS A
Differential protection
128 Busbar protection REB670 2.2 ANSI
Application manual