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CHAPTER 4: SETPOINTS
PROTECTION
889 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUAL
4–131
Generator Unbalance
(46)
Rotor heating in generators may occur due to unbalance (negative sequence) current.
Generators have very specific limits where unbalanced current is concerned (Refer ANSI
C50.13).
The generator unbalance element in 889 has an inverse time overcurrent curve which is
typically used for tripping and a definite time overcurrent curve typically used for alarm
purposes to protect the generator rotor from overheating due to the presence of negative
sequence currents.
For the 889 relay, the inverse time stage operating characteristic is defined by the
following equation:
I
2
= negative sequence current; FLA is the generator rated full load current
K = negative sequence capability constant from the generator manufacturer depending
on size and design
T - time in seconds when I
2
> pickup (minimum 250 ms, maximum defined by setpoint)
NOTE
NOTE:
Unusually high negative sequence current levels may be caused by incorrect phase CT
wiring.
Path
:
Setpoints > Protection > Group 1(6) > Generator > Generator Unbalance
SIGNAL INPUT
Range: CT Bank 1-J1, CT Bank 2-K1
Default: CT Bank 1-J1
This setting provides the selection for the 3-Phase CT bank inputs. This setting allows
applying this element either on terminal side or neutral side of the Generator.
TRIP FUNCTION
Range: Disabled, Trip, Configurable
Default: Disabled
This setting enables the Generator Unbalance Trip functionality. When the Trip function
is selected and the element operates, output relay #1 "Trip" operates but the "ALARM"
LED does not turn on.
When the Configurable function is selected, neither the Trip output, nor the ALARM LED
turns on automatically. They must be configured using their own menus and
FlexLogic
TM
operands.
TRIP PICKUP
Range: 0.00 to 100.00 % FLA in steps of 0.01
Default: 8.00 % FLA
This setting defines the pickup value of the trip element. Pickup value is given in negative
sequence current as percentage of generator rated full load current.
NOTE
NOTE:
This setting should be greater than the corresponding setting for the alarm stage.
CONSTANT K
Range: 0.00 to 100.00 in steps of 0.01
Default: 1.00
This setting is the negative sequence capability constant. This value is normally provided
by the generator manufacturer (see ANSI C50.13) depending on size and design.
Содержание Multilin 889
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Страница 126: ...3 48 889 GENERATOR PROTECTION SYSTEM INSTRUCTION MANUAL SOFTWARE INTERFACE CHAPTER 3 INTERFACES ...
Страница 530: ...4 400 889 GENERATOR PROTECTION SYSTEM INSTRUCTION MANUAL TESTING CHAPTER 4 SETPOINTS ...
Страница 575: ...CHAPTER 8 MAINTENANCE ENVIRONMENTAL HEALTH REPORT 889 GENERATOR PROTECTION SYSTEM INSTRUCTION MANUAL 8 3 ...
Страница 580: ...A 4 889 GENERATOR PROTECTION SYSTEM INSTRUCTION MANUAL REVISION HISTORY CHAPTER A APPENDIX A ...