5–74 489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
FIGURE 5–15: 489 Standard Overload Curves
Note
Above 8.0 × Pickup, the trip time for 8.0 is used. This prevents the overload curve from
acting as an instantaneous element.
The standard overload curves equation is:
(EQ 5.31)
x1
x15
100000
10000
1000
100
10
1.00
0.10 1.00
MULTIPLE OF FULL LOAD AMPS
TIME IN SECONDS
10 100 1000
806804A5.CDR
Time to Trip
Curve Multiplier 2.2116623×
0.02530337
Pickup 1–()
2
× 0.05054758
Pickup 1–()
×+
----------------------------------------------------------------------------------------------------------------------------------------------=
Courtesy of NationalSwitchgear.com
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