GE L90 Instruction Manual page 166

5.5 GROUPED ELEMENTS
• CURRENT DIFF CT TAP 1(2): This setting adapts the remote terminal 1 or 2 (communication channel) CT ratio to the
local ratio if the CT ratios for the local and remote terminals are different. The setting value is determined by
CT / CT
prim_rem prim_loc
rated current). Ratio matching must always be performed against remote CTs and is configured under the
DIFF SIGNAL SOURCE 1
• CURRENT DIFF RESTRAINT 1(2): Selects the bias characteristic for the first (second) slope.
• CURRENT DIFF BREAK PT: This setting is used to select an intersection point between the two slopes.
• CURRENT DIFF DTT: Enables/disables the sending of a DTT by the current differential element on per single-phase
basis to remote relays. To allow the L90 to restart from Master-Master to Master-Slave mode (very important on three-
terminal applications),
• CURRENT DIFF KEY DTT: This setting selects an additional protection element (besides the current differential ele-
ment; for example, distance element or breaker failure) which keys the DTT on a per three-phase basis.
For the current differential element to function properly, it is imperative that all L90 relays on the protected
line have the same firmware revisions.
NOTE
ACTUAL VALUES SETTING
VAG
L90 POWER SYSTEM
XC0 & XC1:
VBG
VCG
Compute Charging
Current
SETTING
CURRENT DIFF SIGNAL
SOURCE 1: CTs ratio
CURRENT DIFF SIGNAL matching
SOURCE 2:
Compute Sum
CURRENT DIFF SIGNAL
of Currents
SOURCE 3:
Compute Local
CURRENT DIFF SIGNAL
Restraint
SOURCE 4:
SETTING
5
L90 POWER SYSTEM
NUM. OF TERMINALS:
"3" = 1
SETTING
L90 POWER SYSTEM
NUM. OF CHANNELS:
"2" = 1
DATA FROM
REMOTE 1
Channel 1 OK=1
Channel 1 ID Fail
ΣIA @Timestamp
2
ΣIB @Timestamp
2
ΣIC @Timestamp
2
AND
DTT PHASE A
DTT PHASE B
AND
DTT PHASE C
AND
DATA FROM
REMOTE 2
Channel 2 OK=1
Channel 2 ID Fail
ΣIA @Timestamp
2
ΣIB @Timestamp
2
ΣIC @Timestamp
2
AND
DTT PHASE A
DTT PHASE B AND
DTT PHASE C AND
SETTING
OR
CURRENT DIFF
BLOCK:
Off
SETTING
CURRENT DIFF
FUNCTION:
Enabled=1
SETTING
CURRENT DIFF
DTT:
Enabled=1
SETTING
CURRENT DIFF
KEY DTT:
Off
5-76
for local and remote terminal CTs (where CT
source. See the Current Differential Settings application example in Chapter 9 for details.
must be set to "Enabled".
CURR DIFF DTT
DATA FROM
LOCAL END
RUN
Charging Current
ΣIA @Timestamp
IA 2
Process
ΣIB @Timestamp Phasors
IB 2
Computations IC
ΣIC @Timestamp
IC 2
CLOCK SYNCHRO-
AND
NIZATION SYSTEM
Clock Are Synchronized
OR
Phase & Frequency
Locked Loop PFLL is OK
AND
OR
AND
OR
AND
AND
OR
OR
OR
OR
FLEXLOGIC OPERAND
STUB BUS OP
Figure 5–35: CURRENT DIFFERENTIAL SCHEME LOGIC
L90 Line Differential Relay
/ CT
prim_rem
RUN
IA
Compute Phasors
IA
IB
& Variance (Local)
IB
IC
SETTINGS
FLEXLOGIC OPERANDS
CURRENT DIFF
50DD SV
PICKUP:
CURRENT DIFF
RESTRAINT 1:
CURRENT DIFF
SETTING
RESTRAINT 2:
CURRENT DIFF
CURRENT DIFF
TAP 1:
BREAK PT:
RUN
IA
Compute
Phasors
IB
& Variance
(Remote 1)
IC
SETTING
CURRENT DIFF
TAP 2:
RUN
IA
Compute
AND RUN
Phasors
IB
& Variance
(Remote 2)
IC
AND
AND
AND
AND
AND
5 SETTINGS
is referred to as the CT primary
prim_loc
OR
2
IA Operate
>1
2
IA Restraint
2
IB Operate
>1
2
IB Restraint
2
IC Operate
>1
2
IC Restraint
OR
AND
OR
AND
OR
AND
OR
CURRENT
To Remote Relays
channel 1 & 2
FLEXLOGIC OPERANDS
87L DIFF OP
87L DIFF OP A
87L DIFF OP B
87L DIFF OP C
87L DIFF RECVD DTT A
87L DIFF RECVD DTT B
87L DIFF RECVD DTT C
87L DIFF PFLL FAIL
87L DIFF CH1 FAIL
87L DIFF CH2 FAIL
87L DIFF CH1 LOSTPKT
87L DIFF CH2 LOSTPKT
87L DIFF CH1 CRCFAIL
87L DIFF CH2 CRCFAIL
87L DIFF CH1 ID FAIL
87L DIFF CH2 ID FAIL
87L DIFF BLOCKED
87L DIFF KEY DTT
To Remote Relays
channel 1 & 2
DTT PHASE A
DTT PHASE B
DTT PHASE C
827056AA.CDR
GE Multilin