Siemens SIPROTEC 7SS52, Operation Manual

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6 - 49
Siemens AG
⋅
May 1998
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D For the purpose of testing the pick-up characteriĆ
stic for the bus-selective function of the protecĆ
tion system, two bays (no sectionalizers or bus
couplers) with identical normalizing factor (identical
current transformer ratio) are connected to the
same busbar (if necessary by simulation of isolator
status). A different test set-up is required for the
check zone (6.5.2.3).
D The test currents are injected directly into the bay
units' measuring inputs. The nominal current of
the bay unit is 1A or 5A, depending on the version.
Fig 6.2 illustrates the set-up for the bus-section
specific protection.
The test set is disconnected by the feeder trip sigĆ
nals.
The test set-up for the check zone is illustrated in
Fig 6.3.
If bus-selectivity is to be tested, then a few bays
can be connected to the second bus (if necessary
by simulation of isolator status).
" $ !!
The check zone must be set more sensitive than the
bus-section specific protection, so that the release
from the check zone is issued before the release
from the bus-section specific protection.
Example:
The characteristic for the bus-section specific protecĆ
tion with diff-current limit ( ) =
2.0
no
and stabilizing factor ( ) = 0.8
should be tested.
The setting for the check zone is then: diff-current
limit ( ) = 0.5
no
and stabilizing factor
( ) = 0.5.
Settings:
D The diff-current supervision must be switched off,
i.e. the parameter DIFF SUPERV ( ).
must be changed over to "inactive" so that the
diff-current supervision does not block the protecĆ
tion during testing.
D The differential current limit and the stabilizing facĆ
tor must be set as required for the bus-section
specific protection and the check zone.
D The overcurrent limits " >TRIP" for the related
bays (block 65) have to be set to 0.
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