Siemens SIPROTEC 7SJ531 - Page 55

-ETHOD OF OPERATION3*
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 &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
IE ENERGIZE INPUT TO BLOCK OR THE NOR
MALLY CLOSED
IE 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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