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CONTROL
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FUNCTION
Range: Disabled, Close, Alarm, Latched Alarm, Configurable
Default: Disabled
Output relay #2 "Close" operates only when the Close function is selected, the element
operates, and Synchrocheck supervision is applied. The "ALARM" LED does not turn on if
the element operates when set to function Close.
INITIATION
Range: Off, Underfreq 1 OP, Underfreq 2 OP, Underfreq 3 OP, Underfreq 4 OP, or FreqRate1
DWN OP
Default: Off
The setpoint selects the FlexLogic operand that initiates the UF Restore scheme; typically
the operate signals from Underfrequency or Frequency Rate of Change functions.
MINIMUM VOLTAGE
Range: 0.000 to 1.250 x VT in steps of 0.001 x VT
Default: 0.900 x VT
The setting sets the minimum voltage for Underfrequency Restoration element
operation specified per times VT.
If the initial frequency is measured from a 3-phase delta connected VT, the positive
sequence voltage is used as the supervision voltage. In such condition, the true supervision
level is internally changed to 1/sqrt(3) of the user setting since the base of VT here is the
phase-phase voltage.
The voltage signal is configured in the FREQUENCY INPUT setting in the UF element which
is used to initiate the Restoration element.
MINIMUM FREQUENCY
Range: 20.00 to 65.00 Hz in steps of 0.01 Hz
Default: 59.90 Hz
The setting sets the minimum frequency to allow the Underfrequency Restoration
element to operate.
The voltage and frequency used here should be associated with the initiation signal. For
example, if the UF restore scheme is triggered by Underfreq 1 OP, the voltage and
frequency values in the 'Underfrequency 1' element should be applied.
RESTORE DELAY
Range: 0.000 to 6000.000 s in steps of 0.001 s
Default: 10.000 s
The setting provides a definite restore time delay. Instantaneous operation is selected by
a restore time delay setting of 0.000 s.
INCOMPLETE SEQUENCE TIME
Range: 1 to 10000 min in steps of 1 min
Default: 100 min
This setting provides a definite reset time delay.
SYNCHROCHECK SUPERVISION
Range: Bypass, Sync1 Close Perm
Default: Bypass
The setpoint selects Synchrocheck supervision. The closing signal (for output #2 only)
from the UF Restore function can be supervised by the Synchrocheck function. The
Synchrocheck function has to be enabled and set accordingly. For applications where
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
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