4–220 845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
PROTECTION CHAPTER 4: SETPOINTS
Figure 4-81: Volts-Per-Hertz Curves for Inverse Curve B
Inverse Curve C:
The curve for the Volts/Hertz Inverse Curve C shape is derived from the formula:
where: T = Operating Time
TDM = Time Delay Multiplier (delay in seconds)
V = fundamental RMS value of voltage (pu)
F = frequency of voltage signal (pu)
Pickup = volts-per-hertz pickup setpoint (pu)
The Volts/Hertz Inverse C curves are shown below.
Figure 4-82: Volts-Per-Hertz Curves for Inverse Curve C
Pickup
F
V
when
Pickup
)
V
TDM
T !
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