ABB REB670 Applications Manual page 116

Section 6
Differential protection
110
N.O.
N.C.
IEC06000085 V1 EN
Figure 41: Scheme2_INX
Circuit breaker replica
The circuit breaker position from a bay shall be given to the busbar protection when the
position of this particular breaker can influence the busbar protection operation. Typical
examples are Blind Spot protection in Bus-section and Bus-coupler bays or End Fault
Protection in feeder bays. In both cases the measuring range of a busbar protection is
limited by the CT location. By additionally recording the CB position of a feeder or a
coupler the zone between the CT and the CB can be better protected while CB is open.
However in such cases it is of utmost importance to connect the CB closing command to
the busbar protection in order to include again the CT current to the busbar protection
zones in time. It is as strongly recommended to always use Scheme1_RADSS for all CBs
positions connected to the IED in order to minimize any risk of possible problems due to
late inclusion of CT current to the relevant differential zones.
Line disconnector replica
The line disconnector position from a feeder bay might be required for busbar protection
under certain circumstances. Typical example is when the line disconnector 989 and
associated grounding switch QC1 are located between CT and protected busbar as
indicated in figure 42.
closed
open
BBP
1
input „closed"
0
1
input „open"
0
current
1
assignment
0
1) disconnector supervision running
2) BI „closed" should change before arcing distance
1MRK 505 337-UUS -
arcing possible
2)
1)
1)
en06000085.vsd
Application manual