Loss Of Excitation - GE 489 Instruction Manual

4.7 S6 VOLTAGE ELEMENTS
PATH: SETPOINTS S6 VOLTAGE ELEMENTS

LOSS OF EXCITATION

[ENTER] for more
4
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
reactance x' / 2. Typically the smaller circle (if used) is set to minimum time with a diameter set to 0.7x
d
x' / 2. This feature is blocked if voltage supervision is enabled and the generator voltage is above the
d
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 = secondary phase-to-phase loss of excitation impedance
loe
∠θ
M = Secondary impedance phasor (magnitude and angle)
loe loe
All relay quantities are in terms of secondary impedances. The formula to convert primary impedance quantities to second-
ary impedance quantities is provided below.
4-42
LOSS OF EXCITATION
ð
ENABLE VOLTAGE
ENTER
ð
ESCAPE SUPERVISION: Yes
VOLTAGE
ESCAPE
LEVEL: 0.70 x Rated
MESSAGE
CIRCLE 1
ESCAPE
TRIP: Off
MESSAGE
ASSIGN CIRCLE 1 TRIP
ESCAPE
RELAYS (1-4): 1---
MESSAGE
CIRCLE 1
ESCAPE
DIAMETER: 25.0 Ωsec
MESSAGE
CIRCLE 1
ESCAPE
OFFSET: 2.5 Ωsec
MESSAGE
CIRCLE 1 TRIP
ESCAPE
DELAY: 5.0 s
MESSAGE
CIRCLE 2
ESCAPE
TRIP: Off
MESSAGE
ASSIGN CIRCLE 2 TRIP
ESCAPE
RELAYS (1-4): 1---
MESSAGE
CIRCLE 2
ESCAPE
DIAMETER: 35.0 Ωsec
MESSAGE
CIRCLE 2
ESCAPE
OFFSET: 2.5 Ωsec
MESSAGE
CIRCLE 2 TRIP
ESCAPE
DELAY: 5.0 s
MESSAGE
V
AB
Z --------------- M
= =
loe
I I
–
A B
Z
primary
Z --------------------------------------------------
=
sec ondary
VT Ratio
489 Generator Management Relay
Range: Yes, No
Range: 0.70 to 1.00 × Rated in steps of 0.01. Seen only if
ENABLE VOLTAGE SUPERVISION
Range: Off, Latched, Unlatched
Range: Any combination of Relays 1 to 4
Range: 2.5 to 300.0 Ωsec in steps of 0.1
Range: 1.0 to 300.0 Ωsec in steps of 0.1
Range: 0.1 to 10.0 s in steps of 0.1
Range: Off, Latched, Unlatched
Range: Any combination of Relays 1 to 4
Range: 2.5 to 300.0 Ωsec in steps of 0.1
Range: 1.0 to 300.0 Ωsec in steps of 0.1
Range: 0.1 to 10.0 s in steps of 0.1
, and the circle offset to the generator transient
d
∠ θ
loe loe
× CT Ratio
4 SETPOINTS
4.7.9 LOSS OF EXCITATION
is "Yes"
and an offset of
d
set-
VOLTAGE LEVEL
(EQ 4.23)
(EQ 4.24)
GE Multilin