GE MI-869 - Page 256

4–138 869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
PROTECTION CHAPTER 4: SETPOINTS
Figure 4-43: Current Unbalance logic diagram
894093A4.cdr
IA RMS IB RMS IC RMS
Calculated Values
Positive seq. Current (I
1
)
IA RMS < 0.02 x CT IB RMS < 0.02 x CT IC RMS < 0.02 x CT
Negative seq. Current (I
2
)
()
RMSICRMSIBRMSIA
avg
I ++´=
3
1
FLA
avg
I
factor
AFLA
avg
Iif
factor
AFLA
avg
Iif
=< =³
,
1,
%100
1
2
Unbal ´´=
factor
A
I
I
RUN
ALARM PICKUP:
SETPOINT
Unbal = Alarm Pickup
I
avg
= 0.25 x FLA Unbal > 40%
OR
AND
OR
2s
0
ALARM PICKUP DELAY:
SETPOINTS
ALARM DROPOUT DELAY: t
PKP
t
RST
SETPOINT
Configurable TRIP FUNCTION:
Disabled=0
Trip
SETPOINT
BLOCK:
Off=0
SETPOINT
LATCH ALARM
ALARM FUNCTION:
Disabled=0
ALARM
OR
AND AND
AND
FLEXLOGIC OPERANDS
SETPOINT
Output Relay X
Do Not Operate, Operate CUR UNBAL ALARM OP
AND AND
OR
LATCH
S R
RESET
Command
LED: Alarm
FLEXLOGIC OPERANDS
SETPOINT
Output Relay X
Do Not Operate, Operate CUR UNBAL TRIP OP
OR
FLEXLOGIC OPERANDS
SINGLE PHASING OP
Operate Output
Relay 1(TRIP)
LED: TRIP
MOTOR FULL LOAD AMPS (FLA)
SETPOINT
From Setpoint > System > Motor
Three Phase Currents
from CT bank
OR
AND
RUN
TRIP CURVE:
SETPOINTS
TRIP PICKUP: TRIP TDM: TRIP RESET TIME:
t
I2/I1
TRIP MAX TIME: TRIP DROPOUT DELAY: TRIP Pickup Delay: TRIP MIN TIME: