ABB REB670 Series Applications Manual page 106

Section 6
Differential protection
N.O.
N.C.
IEC06000085 V1 EN-US
Figure 43: 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 QB9 and
associated earthing switch are located between CT and protected busbar as indicated in
Figure 44.
QB1 QB2
QA1
QB9
BI1
IEC06000086 V1 EN-US
Figure 44: Feeder bay layout when line disconnector position might be required for
Such feeder set-up can be often found in GIS stations where cable CTs are used for busbar
protection. If in such feeder the line disconnector QB9 is open and then immediately the
earthing switch QC1 is closed before the busbar disconnectors QB1 & QB2 are open there is a
100
BBP
input „closed"
input „open"
current
assignment
ZA
ZB
QC1
en06000086.vsd
busbar protection
arcing possible
2)
closed
open
1
0
1)
1
0
1
0
1) disconnector supervision running
2) BI „closed" should change before arcing distance
1MRK 505 370-UEN D
1)
en06000085.vsd
SEMOD127523-79 v3
SEMOD127523-82 v4
Busbar protection REB670
Application manual