9440300990 Rev J
47
DECS-250
Protection
Figure 33. Reverse Power Protection Settings
A
Reverse Power (32R) Pickup (%)
: Adjustable from 0 to 150% in 1% increments.
B
Reverse Power (32R) Time Delay (s)
: Adjustable from 0 to 300 seconds in 0.1 second increments.
C
Reverse Power (32R) Mode
: Select Disabled or Enabled.
Loss of Excitation
The loss of excitation element operates on excessive var flow into the machine, indicating abnormally low
field excitation. This element protects controlled generators as well as motors. A diagram of the 40Q
pickup response is illustrated in Figure 34. BESTCOMS
Plus
settings are described below and shown in
Figure 35.
Generator Protection
During loss of excitation, the generator absorbs reactive power from the power system which can
overheat the stator windings. The loss of excitation element acts on the principal that if a generator begins
to absorb vars outside its steady-state capability curve, it has likely lost its normal excitation supply. The
element is always calibrated to the equivalent three-phase power even if the connection is single-phase.
The loss of excitation element compares the reactive power to a map of the allowed reactive power as
defined by the Pickup setting. The loss of excitation element remains in a pickup condition until power
flow falls below the dropout ratio of 95% of the actual pickup. A time delay is recommended for tripping.
For settings well outside the generator capability curve, adding a 0.5 second time delay helps prevent
transient fault conditions. However, recovery from power system swings after a major fault may take
several seconds. Therefore, if the unit is to pick up near the steady-state capability curve of the generator,
longer time delays are recommended. See Figure 34 for details.
Motor Protection
The DECS-250 compares the real power (kW) flowing into the motor with the reactive power (kvar) being
supplied. Operation of synchronous motors drawing reactive power from the system can result in
overheating in parts of the rotor that do not normally carry current. The 40Q pickup response is shown in
Figure 34.
Содержание DECS-250
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Страница 20: ...4 9440300990 Rev J Introduction DECS 250 ...
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Страница 32: ...16 9440300990 Rev J Voltage and Current Sensing DECS 250 ...
Страница 40: ...24 9440300990 Rev J Synchronizer DECS 250 ...
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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 ...
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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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