GE Multilin 489 Instruction Manual page 188
Generator management relay
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Also See for Multilin 489:
- Instruction manual (306 pages) ,
- Communications manual (78 pages) ,
- Instruction manual (259 pages)
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CHAPTER 5: SETPOINTS
limit curve adjusted accordingly. If the VT Connection setpoint is set to none or if a VT fuse
failure is detected, the acceleration thermal limit curve for the minimum allowable voltage
will be used.
The voltage dependent overload curve is comprised of the three characteristic thermal
limit curve shapes determined by the stall or locked rotor condition, acceleration, and
running overload. The curve is constructed by entering a custom curve shape for the
running overload protection curve. Next, a point must be entered for the acceleration
protection curve at the point of intersection with the custom curve, based on the minimum
allowable starting voltage as defined by the minimum allowable voltage. Locked Rotor
Current and safe stall time must also be entered for that voltage. A second point of
intersection must be entered for 100% voltage. Once again, the locked rotor current and
the safe stall time must be entered, this time for 100% voltage. The protection curve that is
created from the safe stall time and intersection point will be dynamic based on the
measured voltage between the minimum allowable voltage and the 100% voltage. This
method of protection inherently accounts for the change in speed as an impedance relay
would. The change in impedance is reflected by machine terminal voltage and line current.
For any given speed at any given voltage, there is only one value of line current.
5–78
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
Courtesy of NationalSwitchgear.com
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