GE 845 Instruction Manual page 348

PROTECTION
4–220
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:
T
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
TDM
when
1 2 /
V
1
Pickup
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
V
Pickup
F