ABB RELION 670 Series Applications Manual page 146

Section 6
Differential protection
This means that if 722.5 primary amperes is injected only in phase C of any of the connected main
CTs, the IED shall display the differential current of 1250A (primary) and should be on the point of
the pickup (that is, trip).
In addition to busbar protection differential zones, the IED can incorporate other additional
functions and features. If and how they can be used together with summation busbar protection
design is shown in table 25:
Table 25:
Functions
Busbar Differential Protection
Dynamic Zone Selection feature
CCRBRF/CCSRBRF function
OC4PTOC/PHS4PTOCfunction
OC4PTOC/PHS4PTOC function
DRPRDRE function
DRPRDRE function
Table continues on next page
140
Functions
Comment
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 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.
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.
Breaker Fail Protection function will be connected to the summated bay
current. Therefore it will have different pickup level depending on the
type of fault and involved phase(s). See table
be possible to have individual initiation per phase, but only three-phase
initiation can be effectively used. However, if all these limitations are
acceptable it is still possible to use internal CCRBRF/CCSRBRF functions.
Overcurrent Protection function will be connected to the summated bay
current. Therefore, it will have different pickup level depending on the
type of fault and involved phase(s). See table
will be very difficult to insure proper pickup 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.
End Fault Protection feature will be connected to the summated bay
current. Therefore it will have different pickup level depending on the
type of fault and involved phase(s). See table
OC4PTOC/PHS4PTOC do not need any pickup or time coordination with
any other overcurrent protection. Thus if above limitations are
acceptable OC4PTOC/PHS4PTOC can be used with summation design.
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.
Event List feature in the IED can be used in the exactly the same way as
with phase segregated design.
1MRK 505 337-UUS A
SEMOD127594-37 v3
24 for more info. It will not
24 for more info. Thus it
24 for more info. However,
Application manual