Overfrequency - GE D90 Plus Instruction Manual
Line distance protection system
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- Instruction manual (688 pages)
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CONTROL ELEMENTS
Overfrequency
314
Reset Delay
Range: 0.000 to 65.535 seconds in steps of 0.001
Default: 2.000 seconds
This setting specifies a time delay on dropout for the duration between the operate
output state and the return to logic 0 after the input transits outside the defined pickup
range.
Block
Range: any FlexLogic™ operand or shared operand
Default: OFF
Assertion of the operand assigned to this setting blocks operation of the underfrequency
element.
Events
Range: Enabled, Disabled
Default: Disabled
This setting enables and disables the logging of underfrequency events in the sequence
of events recorder.
The logic for the underfrequency function is shown below.
Figure 252: Underfrequency scheme logic
There are two identical overfrequency elements.
A frequency calculation for a given source is made on the input of a voltage or current
channel, depending on which is available. The channels are searched for the signal input in
the following order:
1.
Voltage channel A.
2.
Auxiliary voltage channel.
3.
Current channel A.
4.
Ground current channel.
The first available signal is used for frequency calculation.
The steady-state frequency of a power system is an indicator of the existing balance
between the generated power and the load. Whenever this balance is disrupted through
the disconnection of significant load or the isolation of a part of the system that has a
surplus of generation, the effect will be an increase in frequency. If the control systems of
the generators do not respond fast enough, to quickly ramp the turbine speed back to
normal, the overspeed can lead to the turbine trip. The overfrequency element can be used
to control the turbine frequency ramp down at a generating location. This element can
also be used for feeder reclosing as part of the after load shedding restoration.
Select the Settings > Protection > Control > Overfrequency menu item to open the
overfrequency settings window.
PLUS
D90
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 7: PROTECTION
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