GE 489 - Manual (Page 113)

GE Multilin 489 Generator Management Relay 4-63
4 SETPOINTS 4.10 S9 THERMAL MODEL
4
The 489 takes the information provided and create protection curves for any voltage between the minimum and 100%. For
values above the voltage in question, the 489 extrapolates the safe stall protection curve to 110% voltage. This current
level is calculated by taking the locked rotor current at 100% voltage and multiplying by 1.10. For trip times above the 110%
current level, the trip time of 110% will be used (see the figure below).
Figure 4–15: VOLTAGE DEPENDENT OVERLOAD PROTECTION CURVES
The safe stall curve is in reality a series of safe stall points for different voltages. For a given voltage, there can be
only one value of stall current, and therefore only one safe stall time.
489
VOLTAGE DEPENDENT
OVERLOAD PROTECTION CURVES
808831A3.CDR
1
1 2 3 4 5 6 7 8
2
3
4
5
6
7
8
9
10
20
30
40
50
60
70
80
90
100
T
IM
E
TO
T
R
IP
(S
E
C
O
N
D
S
)
MULTIPLES OF FULL LOAD AMPS
200
300
400
500
600
700
800
900
1000
Acceleration Intersect at 80%V
Custom Curve
Acceleration Intersect at 100%V
Safe Stall Time at 80%V,
80%V Stall Current
Safe Stall Time at 100%V,
100%V Stall Current
Safe Stall Points
Extrapolated to 110%V
GE Multilin
NOTE