GE 745 Instruction Manual page 183

CHAPTER 5: SETPOINTS
745 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
The curve for the inverse curve 3 shape is derived from the formula:
T
=
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)
10000
1000
100
10
1
0.1
1.00
FIGURE 5–37: Volts per hertz scheme logic
D V
------------------------------------ - -- - >
when
F
0.5
V F ⁄
 
--------------- - 1
–
 
Pickup
1.20 1.40 1.60
Multiples of Voltz/Hertz Pickup
FIGURE 5–36: Volts per hertz curve 3
S4 ELEMENTS
Pickup
Time
Delay
Setting
ò
10
3
1
0.3
0.1
1.80 2.00
(EQ 5.14)
5–87