When the bus coupler/section breaker is open, to disconnect this current from both zones,
additional configuration logic is required by using the binary input, for example
ZEROCUR in
two-zone differential protections . Figure
provides an example of such logic. Moreover, the
following two binary inputs are at least necessary in order to guaranty proper operation of
such logic:
•
Normally closed contact of the bus section or bus coupler circuit breaker
•
Signal from the bus section or bus coupler circuit breaker closing circuit that somebody
wants to close the breaker.
This solution does not depend on contact timing between the main contacts and auxiliary
contact of the circuit breaker. It directly follows the philosophy used for RADSS/REB 103
schemes used for similar applications before. Principle connection between the bus-coupler
CB normally closed auxiliary contact (“b” contact), REB670 and internal configuration logic, as
.
en06000155.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
QB1
QB2
b
BI1
2400/1
QA1
ZEROCUR
BIM
CB Closing
Signal
³
1
t
t=1s
&
IEC06000155 V1 EN-US
Figure 47: 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
Section 6
1MRK 505 370-UEN D
Differential protection
104
Busbar protection REB670
Application manual
Summary of Contents for REB670 Series
Page 1: ...Relion 670 SERIES Busbar protection REB670 Version 2 2 IEC Application manual ...
Page 2: ......
Page 22: ...16 ...
Page 64: ...58 ...
Page 226: ...220 ...
Page 244: ...238 ...
Page 358: ...352 ...
Page 392: ...386 ...
Page 398: ...392 ...
Page 436: ...430 ...
Page 454: ...448 ...
Page 466: ...460 ...
Page 474: ...468 ...
Page 475: ...469 ...