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CHAPTER 6: SETPOINTS
Overfrequency (81O)
350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
The relay is equipped with two Overfrequency elements per setpoint group, ANSI device
number 81O-1, and 81O-2. Voltage channel phase A is used for frequency measurement.
The steady-state frequency of a power system is an indicator of the existing balance
between generated power and the load. Whenever this power is disrupted through
disconnection of significant load or the isolation of a part of the system that has surplus of
generation, it would result in increase of frequency. If the control system of the generators
do not respond fast enough to quickly ramp the turbine frequency back to normal, the
overspeed can lead to turbine trip. The overfrequency elements can be used to control the
turbine frequency at a generating location. This element can also be used for feeder
reclosing as part of the "after load shedding restoration"
The following path is available using the keypad. For instructions on how to use the
keypad, please refer to Chapter 3 - Working with the Keypad.
PATH:
SETPOINTS > S3 PROTECTION > SETPOINT GROUP 1(2) > OVER-FREQUENCY1(2)
OVERFREQ 1(2) FUNCTION
Range: Disabled, Alarm, Latched Alarm, Trip
Default: Disabled
For details see
Common
OVERFREQ 1(2) PKP
Range: 40.00 to 70.00 Hz in steps of 0.01
Default: 60.50 Hz
This setting defines the Overfrequency pickup level, and it is usually set to a frequency
level considered dangerous for the stability of the system.
OVERFREQ 1(2) DELAY
Range: 0.1 to 600.0 s in steps of 0.1
Default: 2.0 s
This setting specifies the time delay before overfrequency operation.
OUTPUT RELAY X
For details see
Common
BLOCK 1/2/3
For details see
Common
setpoints.
setpoints.
setpoints.
S3 PROTECTION
6–89
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