Table 25: Functions
Functions Comment
Busbar Differential Protection Differential Protection, Sensitive differential protection, OCT
algorithm, Check Zone and Differential Supervision features will be
connected to the summated bay currents. Therefore, they will have
different start level depending on the type of fault and involved
phase(s). For more information, refer to Table 24. However, if all
these limitations are acceptable it is still possible to use all these
internal busbar protection features. Note that OCT operating logic
will not work properly in case of opening or shorting the main CT
secondary leads (that is, in-between main CT and ASCT). In case of
opening or shorting the ASCT secondary leads (that is, in-between
ASCT and the IED) the OCT logic will operate correctly.
Dynamic Zone Selection feature Zone Selection feature in the IED can be used in the exactly same
way as with phase segregated design. All built-in features, even
including breaker failure protection, protection back-up trip
command routing, EnFP logic can be used in the exactly same way
as for phase segregated design.
CCRBRF/CCSRBRF function Breaker Fail Protection function will be connected to the summated
bay current. Therefore it will have different start level depending on
the type of fault and involved phase(s). See Table 24 for more info. It
will not be possible to have individual starting per phase, but only
three-phase starting can be effectively used. However, if all these
limitations are acceptable it is still possible to use internal CCRBRF/
CCSRBRF functions.
OC4PTOC/PHS4PTOCfunction Overcurrent Protection function will be connected to the summated
bay current. Therefore, it will have different start level depending on
the type of fault and involved phase(s). See Table 24 for more info.
Thus it will be very difficult to insure proper start and time grading
with downstream overcurrent protection relays. Hence it will be
quite difficult to use OC4PTOC/PHS4PTOC as backup feeder
protection with summation design.
OC4PTOC/PHS4PTOC function End Fault Protection feature will be connected to the summated bay
current. Therefore it will have different start level depending on the
type of fault and involved phase(s). See Table 24 for more info.
However, OC4PTOC/PHS4PTOC do not need any start or time
coordination with any other overcurrent protection. Thus if above
limitations are acceptable OC4PTOC/PHS4PTOC can be used with
summation design.
DRPRDRE function Disturbance Recording feature will be connected to the individual
summated bay current. Therefore recorded currents will not
correspond to any actual primary currents. However such DRPRDRE
records can still be used to evaluate internal busbar protection,
CCRBRF/CCSRBRF and OC4PTOC/PHS4PTOC protections
operation.
DRPRDRE function Event List feature in the IED can be used in the exactly the same way
as with phase segregated design.
DRPRDRE function Trip Value Recording feature will be connected to the individual
summated bay current. Therefore recorded trip current values will
not correspond to any actual primary currents. However such
records can still be used to evaluate internal busbar protection,
CCRBRF/CCSRBRF and OC4PTOC/PHS4PTOC protections
operation.
Communication All communication features in the IED can be used in the exactly the
same way as with phase segregated design
SMBRREC function Autoreclosing function in the IED can be used in the exactly same
way as with phase segregated design.
Section 6 1MRK 505 370-UEN D
Differential protection
140 Busbar protection REB670
Application manual
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