-ETHOD OF OPERATION
3*
6
# ' #
&AST BUS BAR PROTECTION USING
REVERSE INTERLOCKING SCHEME
%ACH OF THE OVERCURRENT STAGES CAN BE BLOCKED VIA
BINARY INPUTS OF THE RELAY ! SETTING PARAMETER DETER
MINES WHETHER THE BINARY INPUT OPERATES IN THE NOR
MALLY OPEN IE ENERGIZE INPUT TO BLOCK OR THE NOR
MALLY CLOSED IE ENERGIZE INPUT TO RELEASE MODE
4HUS THE OVERCURRENT TIME PROTECTION CAN BE USED
AS FAST BUSBAR PROTECTION IN STAR CONNECTED NET
WORKS OR IN OPEN RING NETWORKS RING OPEN AT ONE LO
CATION USING THE REVERSE INTERLOCK PRINCIPLE 4HIS
IS USED IN HIGH VOLTAGE SYSTEMS IN POWER STATION
AUXILIARY SUPPLY NETWORKS ETC IN WHICH CASES A
TRANSFORMER FEEDS FROM THE HIGHER VOLTAGE SYSTEM
ONTO A BUSBAR WITH SEVERAL OUTGOING FEEDERS REFER TO
&IGURE
2EVERSE INTERLOCKING MEANS THAT THE OVERCURRENT
TIME PROTECTION CAN TRIP WITHIN A SHORT TIME 4 )
WHICH IS INDEPENDENT OF THE GRADING TIME IF IT IS NOT
BLOCKED BY PICK UP OF ONE OF THE NEXT DOWNSTREAM
OVERCURRENT TIME RELAYS &IGURE 4HEREFORE THE
PROTECTION WHICH IS CLOSEST TO THE FAULT WILL ALWAYS TRIP
WITHIN A SHORT TIME AS IT CANNOT BE BLOCKED BY A RELAY
BEHIND THE FAULT LOCATION 4HE TIME STAGES ) OR )
P
OP
ERATE AS DELAYED BACK UP STAGES
)
4 )
4 )
)
)
)
T
T
4RIP
4RIP
4RIP
4RIP
)NFEED DIRECTION
!
"
T
4 )
4 )
T
&AULT LOCATION !
TRIPPING TIME 4 )
&AULT LOCATION "
TRIPPING TIME T
BACK UP TIME 4 )
"LOCK )
&IGURE
"USBAR PROTECTION USING REVERSE INTERLOCKING PRINCIPLE
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