GE Power Management
489 Generator Management Relay 4-29
4 SETPOINT PROGRAMMING 4.7 S6 VOLTAGE ELEMENTS
4
4.7 S6 VOLTAGE ELEMENTS 4.7.1 UNDERVOLTAGE
The undervoltage elements may be used for protection of the generator and/or its auxiliary equipment during prolonged
undervoltage conditions. They are active only when the generator is online. The alarm element is definite time and the trip
element can be definite time or a curve. When the magnitude of the average phase-phase voltage is less than the pickup ×
the generator rated phase-phase voltage, the element will begin to time out. If the time expires, a trip or alarm will occur.
UNDERVOLTAGE
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UNDERVOLTAGE
ALARM: Off
Range: Off, Latched, Unlatched
ASSIGN ALARM
RELAYS (2-5): ---5
Range: Any combination of Relays 2 to 5
UNDERVOLTAGE ALARM
PICKUP: 0.85 x Rated
Range: 0.50 to 0.99
×
Rated in steps of 0.01
UNDERVOLTAGE ALARM
DELAY: 3.0 s
Range: 0.2 to 120.0 s in steps of 0.1
UNDERVOLTAGE ALARM
EVENTS: Off
Range: On, Off
UNDERVOLTAGE
TRIP: Off
Range: Off, Latched, Unlatched
ASSIGN TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to 4
UNDERVOLTAGE TRIP
PICKUP: 0.80 x Rated
Range: 0.50 to 0.99
×
Rated in steps of 0.01
UNDERVOLTAGE TRIP
DELAY: 1.0 s
Range: 0.2 to 10.0 s in steps of 0.1
UNDERVOLTAGE CURVE
RESET RATE: 1.4 s
Range: 0.0 to 999.9 s in steps of 0.1
UNDERVOLTAGE TRIP
ELEMENT: Curve
Range: Curve, Definite Time
The curve reset rate is a linear reset time from the threshold
of trip. If the VT type is selected as None, VT fuse loss is
detected, or the magnitude of
I
1
< 7.5% CT, the undervoltage
protection is disabled. The pickup levels are insensitive to
frequency over the range of 5 to 90 Hz.
The formula for the undervoltage curve is:
where:
T
= trip time in seconds
D
=
UNDERVOLTAGE TRIP DELAY
setpoint
V
= actual per unit phase-phase voltage
V
pickup
=
UNDERVOLTAGE TRIP PICKUP
setpoint
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ESCAPE
T
D
1
VV
pickup
⁄–
------------------------------------= , when
VV
pickup
<
0.1
1
10
100
1000
0 0.2 0.4 0.6 0.8 1
Multiples of Undervoltage Pickup
10
3
1
0.3
TIME DELAY SETTING
Time to Trip (seconds)
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