GE MI-869 - Page 229

CHAPTER 4: SETPOINTS PROTECTION
869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL 4–111
Figure 4-31: Percent Differential logic diagram
89$1.cdr
Ibd –r*
STARTING
*Ibr >pickup
Iad– r*
STARTING
*Iar > pickup
SETPOINT
Phase A current (Ia)
SETPOINT
FUNCTION Disabled Trip
Pickup
AND
Phase B current (Ib) Phase C current (Ic)
RUN
TRIP
LED: PICKUP
OR
Neutral side currents (I
ns
)
(K1-CT) Bank
SETPOINT
BLOCK Off = 0
OR
AND
Configurable
SETPOINTS
Output Relays Do Not Operate, Operate
LED: TRIP
Percent Diff PKP C
FlexLogic Operands
Phase A current (Ia) Phase B current (Ib) Phase C current (Ic)
Terminal side currents (I
ts
)
(J1-CT) Bank
I
ar
I
br
I
cr
Restraint
Phasors
I
ad
I
bd
I
cd
Differential
Phasors
Break 2 Slope 2 Slope 1 Break 1
Percent Diff PKP A
FlexLogic Operands
Percent Diff PKP
FlexLogic Operands
Percent Diff PKP B
FlexLogic Operands
Percent Diff OP C
FlexLogic Operands
Percent Diff OP A
FlexLogic Operands
Percent Diff OP
FlexLogic Operands
Percent Diff OP B
FlexLogic Operands
Percent Diff Sat C
FlexLogic Operands
Percent Diff Dir C
OR
AND
Percent Diff Sat B
FlexLogic Operands
Percent Diff Dir B
OR
AND
Percent Diff Sat A
FlexLogic Operands
Percent Diff Dir A
OR
AND
OR
SETPOINT
TYPE: Internal Summation
|I
d
| = |I
ts
–I
ns
|
|I
r
| = MAX{|I
ts
|, |I
ns
|}
I
ad
>(0.5 x PKP)
I
bd
>(0.5 x PKP)
I
cd
>(0.5 x PKP)
OR
Percent Diff Warn
FlexLogic Operands
10s
Phase A current (Ia) Phase B current (Ib) Phase C current (Ic)
Core Balance currents (I
dcb
)
(K1-CT) Bank
Phase A current (Ia) Phase B current (Ib) Phase C current (Ic)
Terminal side currents (I
ts
)
(J1-CT) Bank
SETPOINT
TYPE: Core Balance
I
r
= | I
p
|
I
d
= | I
dcb
|
0s
Restraint
Phasors
Differential
Phasors
RUN
Icd– r*
STARTING
*Icr > pickup
RUN
T
pkp
0
T
pkp
0
T
pkp
0
SETPOINT
SETPOINT SETPOINT
Restraint Factor Starting (r)
TYPE:
Internal Summation
Core Balance
SETPOINT