Figure 4-57. loss of excitation (40q) -66 โ Basler Electric DGC-2020 User Manual
Page 176
Figure 4-56. Generator Capability Curve vs. 40Q Response
If reactive power is within the 40Q tripping region for the duration of the 40Q activation delay setting
B
, a
loss of excitation condition is annunciated. A loss of excitation annunciation can be user-selected to
trigger a pre-alarm
C
(warning) or alarm
C
(shutdown). A loss of excitation annunciation can also be user-
configured to close a programmable output. The calculation used in the DGC-2020 for the approximate
tripping region is given by:
๐๐๐๐๐๐๐๐ ๐ ๐๐๐๐๐ = 40๐ ๐๐๐๐๐ข๐ + ๏ฟฝ
1
8
๏ฟฝ โ ๏ฟฝ
๐ด๐๐ก๐ข๐๐ ๐๐๐ก๐ก๐ โ 100
๐ ๐๐ก๐๐ ๐ฃ๐๐
๏ฟฝ
where the units of the Tripping Region and the 40Q Pickup setting are percent of rated var.
The hysteresis setting
D
functions as a loss of excitation dropout by preventing rapid switching of the
pickup output.
Activation delays
B
are recommended for tripping. Adding a small delay will help assure that false alarms
do not occur for transient fault conditions or swings in the power system.
The element is disabled when Alarm Configuration is set to โNoneโ. Element status is available in
BESTlogicPlus Programmable Logic when โStatus Onlyโ is selected.
The BESTCOMSPlus Loss of Excitation (40Q) screen is illustrated in Figure 4-57.
Figure 4-57. Loss of Excitation (40Q)
A
Pickup: Adjustable from โ150% to 0% of rated vars in 0.1% increments.
B
Activation Delay: Adjustable from 0 to 30 s in 0.1 s increments.
C
Alarm Configuration: None, Alarm, Pre-Alarm, or Status Only.
D
Hysteresis: Adjustable from 1% to 10% in 0.1% increments.
4-66
DGC-2020 BESTCOMSPlus
ยฎ Software
9400200990 Rev X