GE 745 TRANSFORMER MANAGEMENT RELAY

5-98 745 Transformer Management Relay GE Power Management
5.10 INVERSE VOLTS-PER-HERTZ CURVES 5 SETPOINTS
5
5.10.2 INVERSE CURVE 2
The curve for the inverse curve 2 shape is derived from the formula:
where
T = operate time (seconds)
D = delay setpoint (seconds)
V = fundamental RMS value of voltage (V)
F = frequency of voltage signal (Hz)
Pickup = volts-per-hertz pickup setpoint (V/Hz)
Figure 5–17: INVERSE CURVE 2
T
D
VF
⁄
Pickup
------------------ 1
–
---------------------------
=
when
V
F
----
Pickup
>
0.1
1
10
100
1000
1.00 1.20 1.40 1.60 1.80 2.00
Multiples of Volts/Hertz Pickup
Time
Delay
Setting
10
3
1
0.3
0.1
Time to Trip (seconds)