'(& )( )'& &) ( &!& ")& &$(( $# Ć %&( $# #)" &&#$
4 - 17
Siemens AG ⋅ May 1998
The status of the feeder isolator (Q9) in the outgoing
feeder can be processed by setting the parameter
"ISOL.5" ( ). For the feeder type "outgoĆ
ing feeder", isolator 5 can only be configured "exiĆ
sting" or "non-existing".
If isolator 5 is configured "existing", then the outgoĆ
ing feeder is considered to be allocated to a bus secĆ
tion, if the corresponding bus isolator and the feeder
isolator are CLOSED..
With transfer (bypass) bus operation it is sufficient
that after closing of Q7 either the bus isolator Q1 or
the feeder isolator Q9 is opened (figure 4.11).
BB1
BPB
Q1
Q9
Q7
Figure 4.11 Transfer (bypass) bus operation with closed busbar isolaĆ
tor
With parallel feeders a differential current may occur,
if one feeder was earthed and an earth fault occurs
on the parallel feeder (figure 4.12). The protection
sees a current in the zero sequence system of the
earthed feeder.
Integrating the feeder isolator (Q9) into the the isolaĆ
tor logic prevents spurious tripping by the 7SS52.
Q1 Q9
Z
0M
Figure 4.12 Parallel feeders
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