GE 489 User Manual

4-38 489 Generator Management Relay
GE Power Management
4.7 S6 VOLTAGE ELEMENTS 4 SETPOINT PROGRAMMING
4
4.7.9 LOSS OF EXCITATION
Loss of excitation is detected with an impedance element. When the impedance falls within the impedance circle for the
specified delay time, a trip will occur if it is enabled. Circles 1 and/or 2 can be tuned to a particular system. The larger circle
diameter should be set to the synchronous reactance of the generator,
x
d
, and the circle offset to the generator transient
reactance
x’
d
/ 2. Typically the smaller circle (if used) is set to minimum time with a diameter set to 0.7 x
d
and an offset of
x’
d
/ 2. This feature is blocked if voltage supervision is enabled and the generator voltage is above the
VOLTAGE LEVEL
set-
point. The trip feature is supervised by minimum current of 0.05 × CT. Note that the Loss of Excitation element will be
blocked if there is a VT fuse failure or if the generator is offline. Also, it uses output CT inputs.
The secondary phase-phase loss of excitation impedance is defined as:
where:
Z
loe
= secondary phase-to-phase loss of excitation impedance
M
loe
∠θ
loe
= Secondary impedance phasor (magnitude and angle)
All relay quantities are in terms of secondary impedances. The formula to convert primary impedance quantities to second-
ary impedance quantities is provided below.
where: Z
primary
= primary ohms impedance
CT Ratio = programmed CT ratio, if CT ratio is 1200:5 use a value of 1200 / 5 = 240
VT Ratio = programmed VT ratio, if VT ratio is 100:1 use a value of 100

LOSS OF EXCITATION

[ENTER] for more
ENABLE VOLTAGE
SUPERVISION: Yes
Range: Yes, No
VOLTAGE
LEVEL: 0.70 x Rated
Range: 0.70 to 1.00
×
Rated in steps of 0.01. Seen only if
ENABLE VOLTAGE SUPERVISION is Yes
CIRCLE 1
TRIP: Off
Range: Off, Latched, Unlatched
ASSIGN CIRCLE 1 TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to 4
CIRCLE 1
DIAMETER: 25.0
Ω
sec
Range: 2.5 to 300.0
Ω
sec in steps of 0.1
CIRCLE 1
OFFSET: 2.5
Ω
sec
Range: 1.0 to 300.0
Ω
sec in steps of 0.1
CIRCLE 1 TRIP
DELAY: 5.0 s
Range: 0.1 to 10.0 s in steps of 0.1
CIRCLE 2
TRIP: Off
Range: Off, Latched, Unlatched
ASSIGN CIRCLE 2 TRIP
RELAYS (1-4): 1---
Range: Any combination of Relays 1 to 4
CIRCLE 2
DIAMETER: 35.0
Ω
sec
Range: 2.5 to 300.0
Ω
sec in steps of 0.1
CIRCLE 2
OFFSET: 2.5
Ω
sec
Range: 1.0 to 300.0
Ω
sec in steps of 0.1
CIRCLE 2 TRIP
DELAY: 5.0 s
Range: 0.1 to 10.0 s in steps of 0.1
ENTER
ESCAPE
ð
ð
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
Z
loe
V
AB
I
A
I
B
–
--------------- M
loe
θ
loe
∠==
Z
ondary
sec
Z
primary
CT Ratio×
VT Ratio
--------------------------------------------------=

GE 489 Specifications

General

Brand	GE
Model	489
Category	Relays
Language	English