12-
50
750/760 Feeder Management Relay GE Power Management
12.7 VOLTAGE 12 S5 PROTECTION
12
12.7.3 UNDERVOLTAGE INVERSE TIME DELAY CHARACTERISTICS
The undervoltage elements can be programmed to have an inverse time delay characteristic. The undervolt-
age delay setpoint defines a family of curves as illustrated by the following equation and figure.
where
T
= Operating Time
D
= Undervoltage Delay Setpoint
V
= Voltage as a fraction of the nominal
VT Secondary Voltage
V
pu
= Pickup Level
Note: At 0% of pickup the operating time equals the Undervoltage Delay Setting.
Figure 12–23: INVERSE TIME UNDERVOLTAGE CURVES
T
D
1
VV
pu
⁄
–
--------------------------
=
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
16.0
18.0
20.0
0 102030405060708090100
% of Pickup
Operating Time (s)
D=1.0
D=2.0
D=5.0
D = 1.0D = 2.0
D = 1.0D = 5.0
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