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350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION
CHAPTER 6: SETPOINTS
VOLTAGE MODE
Range: Phase-ground, Phase-phase
Default: Phase-ground
If the Phase VT Connection is set to "Wye", then the Voltage Mode setting further defines
the operating quantity and per-unit value for this element.
When "Phase-ground" is selected, the relay applies the phase-to-ground nominal
voltage programmed as VT Secondary from Voltage Sensing menu.
When "Phase-phase" voltage mode is selected, then the computed phase-phase voltage
as an operating quantity is referenced with respect to the phase-to-phase nominal
voltage, that the relay calculates when multiplying the programmed phase-ground
nominal voltage and the square root of 3.
If the Phase VT Connection (set under
SETPOINTS > S2 SYSTEM SETUP > VOLTAGE SENSING
> VT CONNECTION
is set to "Delta", then the programmed phase-to-phase nominal
voltage is used to define the per-unit value, regardless of the Voltage Mode selection.
PICKUP
Range: 0.80 to 4.00 V/Hz in steps of 0.01 V/Hz
Default: 1.05 x V/Hz
Enter the pickup value (multiple of V/Hz), above which the volts-per-hertz element will
pickup. For example, if Phase VT Secondary and Nominal Frequency are set to 120 V and
60 Hz respectively, and Pickup is set to 1.05 x (V/Hz) then the volts-per-hertz element will
pickup, when the actual division of the measured volts by the detected frequency is above
2.1.
CURVE
Range: Definite Time, Inverse A, Inverse B, Inverse C, FlexCurve A, FlexCurve B
Default: Definite TIme
Definite Time:
For the definite time curve, T(s) = TD multiplier. For example, setting the TD multiplier to
20 results a time delay of 20 seconds to operate when above the Volts/Hz pickup setting.
Inverse Curve A:
The curve for the Volts/Hertz Inverse Curve A shape is derived from the formula:
where:
T = Operating Time
TDM = Time Delay Multiplier (delay in seconds)
V = fundamental RMS value of voltage
F = frequency of voltage signal
Pickup = volts-per-hertz pickup setpoint
