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PROTECTION
4–224
SEMICYCLES SET
Range: 1 to 20 in steps of 1
Default: 3
This setting specifies a SET counter prior to picking up. When the frequency is detected
to be below the setting (and the rate of change is below the setting as well if in the DF/DT
Type), the element starts counting for however many consecutive half-periods (semi
cycles) it continues below the setting. If the SET counter is reached, the pickup signal of
the element is activated and the element starts the delay timer set independently for
each element. However, the invalid frequency measurement will not affect the SET
counter.
SEMICYCLES RESET
Range: 0 to 4 in steps of 1
Default: 0
If the frequency transiently restores and pickup conditions are not satisfied, the element
freezes the SET counter to pick up and starts counting the number of semi cycles to
reset the element. If the count of semi cycles to reset reaches the value set in the setting
SEMICYCLES RESET, then the element is reset. On the other hand, if the pickup conditions
are satisfied before reset, the element will continue the count of semi cycles to set from
where it was left. The invalid frequency measurement will not affect the SET counter.
The SEMICYCLES SET and SEMICYCLES RESET settings are common for the eight Fast
Underfrequency elements.
Path:
Setpoints > Protection > Group 1(6) > Frequency > Fast Underfrequency > Fast
Underfreq1(8)
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
TYPE
Range: UF Only, UF and df/dt
Default: UF Only
This setting specifies the input to the element. The UF ONLY type uses only the frequency
value. The UF and DF/DT type considers both frequency and rate of change of frequency
(df/dt) as the input.
UNDERFREQENCY PICKUP
Range: 20.00 to 65.00 Hz in steps of 0.01 Hz
Default: 59.00 Hz
This setpoint sets the Underfrequency Pickup level.
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
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