46
9440300990 Rev J
Protection
DECS-250
Underfrequency
An underfrequency condition occurs when the frequency of the generator voltage decreases below the
81U pickup threshold
A
for the duration of the 81U time delay setting
B
. A voltage inhibit setting
C
, expressed
as a percentage of the rated generator voltage, can be implemented to prevent an underfrequency trip
from occurring during startup when the generator voltage is rising toward the nominal level.
Underfrequency protection can be enabled and disabled
D
without altering the pickup, delay, and inhibit
settings. Underfrequency pickup and trip elements in BESTlogic
Plus
can be used in a logic scheme to
initiate corrective action in response to the condition. BESTCOMS
Plus
underfrequency settings are
illustrated in Figure 32.
Figure 32. Underfrequency Protection Settings
A
Underfrequency (81U) Pickup (Hz)
: Adjustable from 30 to 70 hertz in 0.01 hertz increments.
B
Underfrequency (81U) Time Delay (s)
: Adjustable from 0.1 to 300 seconds in 0.1 second increments.
C
Underfrequency (81U) Voltage Inhibit (%)
: Adjustable from 50 to 100% in 1% increments.
D
Underfrequency (81U) Mode
: Select Disable or Under.
Power Protection
BESTCOMSPlus Navigation Path:
Settings Explorer, Protection, Power
HMI Navigation Path:
Settings, Protection, Power
Generator power levels are monitored to protect against reverse power flow and loss of excitation.
Reverse Power
Reverse power protection guards against reverse power flow that may result from a loss of prime mover
torque (and lead to generator motoring). A reverse power condition occurs when the flow of reverse
power exceeds the 32R pickup threshold
A
for the duration of the 32R time delay
B
. Reverse power
protection can be enabled and disabled
C
without altering the pickup and time delay settings. Reverse
power pickup and trip elements in BESTlogic
Plus
can be used in a logic scheme to initiate corrective
action in response to the condition. BESTCOMS
Plus
reverse power protection settings are illustrated in
Figure 33.
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Страница 20: ...4 9440300990 Rev J Introduction DECS 250 ...
Страница 28: ...12 9440300990 Rev J Power Stage DECS 250 ...
Страница 32: ...16 9440300990 Rev J Voltage and Current Sensing DECS 250 ...
Страница 40: ...24 9440300990 Rev J Synchronizer DECS 250 ...
Страница 52: ...36 9440300990 Rev J Auxiliary Control DECS 250 ...
Страница 56: ...40 9440300990 Rev J Contact Inputs and Outputs DECS 250 ...
Страница 84: ...68 9440300990 Rev J Limiters DECS 250 ...
Страница 108: ...92 9440300990 Rev J Power System Stabilizer DECS 250 Figure 85 PSS Function Blocks and Software Switches ...
Страница 114: ...98 9440300990 Rev J Power System Stabilizer DECS 250 Figure 96 PSS Parameter Settings ...
Страница 124: ...108 9440300990 Rev J Stability Tuning DECS 250 ...
Страница 126: ...110 9440300990 Rev J Mounting DECS 250 Figure 103 Overall and Projection Mounting Dimensions ...
Страница 127: ...9440300990 Rev J 111 DECS 250 Mounting Figure 104 DECS 250 Escutcheon Plate Dimensions ...
Страница 128: ...112 9440300990 Rev J Mounting DECS 250 Figure 105 Panel Cutting and Drilling Dimensions for DECS 250 Panel Mounting ...
Страница 198: ...182 9440300990 Rev J Timekeeping DECS 250 ...
Страница 210: ...194 9440300990 Rev J CAN Communication DECS 250 ...
Страница 304: ...288 9440300990 Rev J Maintenance DECS 250 ...
Страница 316: ...300 9440300990 Rev J Specifications DECS 250 ...
Страница 334: ...318 9440300990 Rev J Analog Expansion Module DECS 250 ...
Страница 341: ...9440300990 Rev J 325 DECS 250 Contact Expansion Module Figure 188 CEM 2020 Input Contact and Output Contact Terminals ...
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