GE Multilin 489 User Manual

CHAPTER 5: SETPOINTS
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL 5–53
5.7.8 Neutral Undervoltage
PATH: SETPOINTS ZV S6 VOLTAGE ELEM. ZV NEUTRAL U/V (3RD HARMONIC)
Note
The LOW POWER BLOCKING LEVEL, NEUTRAL U/V ALARM LEVEL, and NEUTRAL U/V TRIP
LEVEL setpoints are seen only if the S2 SYSTEM SETUP ZV VOLTAGE ZV VT CONNECTION
setpoint is “Delta”
The neutral undervoltage function responds to 3rd harmonic voltage measured at the
generator neutral and output terminals. When used in conjunction with the Neutral
Overvoltage (fundamental frequency) function, it provides 100% ground fault protection of
the stator windings.
For Wye connected VTs:
Since the amount of third harmonic voltage that appears in the neutral is both load and
machine dependent, the protection method of choice is an adaptive method. If the phase
VT connection is wye, the following formula is used to create an adaptive neutral
undervoltage pickup level based on the amount of third harmonic that appears at the
generator terminals.
(EQ 5.24)
The 489 tests the following permissives prior to testing the basic operating equation to
ensure that V
N3
’ should be of a measurable magnitude for an unfaulted generator:
1 NEUTRAL U/V [Z]
(3rd HARMONIC)
LOW POWER BLOCKING
LEVEL: 0.05 x Rated
Range: 0.02 to 0.99 × Rated MW in
steps of 0.01
MESSAGE
LOW VOLTAGE BLOCKING
LEVEL: 0.75 x Rated
Range: 0.50 to 1.00 × Rated in steps of
0.01
MESSAGE
NEUTRAL UNDERVOLTAGE
ALARM: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN ALARM
RELAYS (2-5): ---5
Range: Any combination of Relays 2 to
5
MESSAGE
NEUTRAL U/V ALARM
LEVEL: 0.5 Vsec
Range: 0.5 to 20.0 Vsec in steps of 0.1
MESSAGE
NEUTRAL UNDERVOLTAGE
ALARM DELAY: 30 s
Range: 5 to 120 s in steps of 1
MESSAGE
NEUTRAL UNDERVOLTAGE
ALARM EVENTS: Off
Range: On, Off
MESSAGE
NEUTRAL UNDERVOLTAGE
TRIP: Off
Range: Off, Latched, Unlatched
MESSAGE
ASSIGN TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to
4
MESSAGE
NEUTRAL U/V TRIP
LEVEL: 1.0 Vsec
Range: 0.5 to 20.0 Vsec in steps of 0.1
MESSAGE
NEUTRAL UNDERVOLTAGE
TRIP DELAY: 30 s
Range: 5 to 120 s in steps of 1
V
N3
V
P3
3⁄()V
N3
+
------------------------------------
0.15 which simplifies to V
P3
17V
N3
≥≤
Courtesy of NationalSwitchgear.com

GE Multilin 489 Specifications

General

Brand	GE
Model	Multilin 489
Category	Relays
Language	English