CHAPTER 5: SETPOINTS S4 ELEMENTS
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 5–87
The curve for the inverse curve 3 shape is derived from the formula:
(EQ 5.14)
where T = operate time (in seconds)
D = delay setpoint (in seconds)
V = fundamental RMS value of voltage (V)
F = frequency of voltage signal (Hz)
Pickup = volts-per-hertz pickup setpoint (V/Hz)
FIGURE 5–36: Volts per hertz curve 3
FIGURE 5–37: Volts per hertz scheme logic
T
D
VF⁄
Pickup
----------------
0.5
1–
-------------------------------------
= when
V
F
---
Pickup>
0.1
1
10
100
1000
10000
1.00 1.20 1.40 1.60 1.80 2.00
Multiples of Voltz/Hertz Pickup
Time
Delay
Setting
ò
3
10
1
0.3
0.1
Time to Trip (seconds)
To Next Page
Loading...
