GE 750 Instruction Manual page 161

S5 Protection
NOTE
BUS
UNDERVOLTAGE 1
GE Multilin
overfrequency, have their own inhibit functions independent of the undervoltage
protection features.
• Source Transfer Schemes: In the event of an undervoltage, a transfer signal
may be generated to transfer a load from its normal source to a standby or
emergency power source.
The undervoltage elements can be programmed to have an inverse time delay
characteristic. The undervoltage delay setpoint defines a family of curves as shown
below. The operating time is given by:
where: T = Operating Time
D = Undervoltage Delay setpoint
V = Voltage as a fraction of the nominal VT Secondary Voltage
V = Pickup Level
pu
At 0% of pickup, the operating time equals the Undervoltage Delay setpoint.
20.0
18.0
16.0
14.0
12.0
10.0
8.0
6.0
4.0
2.0
0.0
FIGURE 5–27: Inverse Time Undervoltage Curves
b) Bus Undervoltage
PATH: SETPOINTS S5 PROTECTION
[ ] BUS UNDERVOLTAGE 1
FUNCTION: Disabled
BUS UNDERVOLTAGE 1
MESSAGE
RELAYS (3-7): -----
BUS UNDERVOLTAGE 1
MESSAGE
PICKUP: 0.75 x VT
BUS UNDERVOLTAGE 1
MESSAGE
CURVE: Definite Time
BUS UNDERVOLTAGE 1
MESSAGE
DELAY:
PHASES REQUIRED FOR
MESSAGE
OPERATION: All Three
MIN OPERATING
MESSAGE
VOLTAGE: 0.30 x VT
Bus Undervoltage 1 and 2 are identical elements that generate outputs in response
to undervoltage conditions on the bus voltage inputs. The time delay characteristic
can be programmed as definite time or inverse time. A minimum operating voltage
http://www.GEmultilin.com
D
T
= --------------------------- -
1 V V ⁄
–
pu
D=5.0 2.0 1.0
0 10 20 30 40 50 60 70 80 90 100 110
% of V pickup
VOLTAGE BUS UNDERVOLTAGE 1(2)
Range: Disabled, Trip, Alarm, Latched
Range: Any combination of 3 to 7
Range: 0.00 to 1.25 x VT in steps of
Range: Definite Time, Inverse Time.
Range: 0.0 to 6000.0 s in steps of 0.1
2.0 s
Range: Any One, Any Two, All Three
Range: 0.00 to 1.25 x VT in steps of
750/760
Feeder Management Relay
(EQ 5.17)
Alarm, Control
Auxiliary relays
0.01
0.01
5–65