en06000155_ansi.vsd
Zone A
Zone B
Bus-Coupler
Bay
REB 670
CTRLZA
CTRLZB
TRIP
CONNZA
CONNZB
Bxxx
I3PB1
BLKTR
TRZONE
TRBAY
BBP & BFP trip command to Bus-Coupler breaker
BOM
A/D
Parameter ZoneSel must
be set to "FixedToZA&-ZB"
tZeroCurrent=150ms
Other
Equipment
CT Input
TRM
External or Internal
Bus-Coupler BFP
Backup Trip Command
Bus-Coupler Backup
OC Trip
189
289
BI1
ZEROCUR
BIM
CB Closing
Signal
t
t=1s
b
152
AND
OR
ANSI06000155 V1 EN-US
Figure 48:
Bus coupler bay with one CT and “b” aux. contact only from CB
This scheme will disconnect the section/coupler CTs after a pre-set time length (≥80
ms recommended) defined by the parameter setting
tZeroCurrent
in the relevant bay
function block from the moment of opening of the section/coupler CB (that is, from the
moment when auxiliary "b" contact operates). Nevertheless this time delay is
absolutely necessary in order to prevent racing between the opening of the main
breaker contact and disconnection of the CT from the differential zones. This scheme
will as well disconnect the CT in case of the operation of any of the two internal
differential zones used in the scheme. This will secure the delayed (≥150 ms,
depending one the values of the setting
tZeroCurrent
) clearing and tripping of the
internal fault within the blind zone even in case of section/coupler circuit breaker
failure during such fault. This facility will improve the performance of the busbar
protection scheme when one CT is located on only one side of the bus-section / bus-
coupler circuit breaker.
With GIS or live tank circuit breakers, owing to high cost of HV CT installations,
sometimes no current transformers are available in bus-section or bus-coupler bay. This
is the third solution shown in Figure
1MRK 505 370-UUS A
Section 6
Differential protection
Busbar protection REB670 2.2 ANSI
125
Application manual
Summary of Contents for RELION REB670
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