58
9440300990 Rev J
Limiters
DECS-250
Figure 43. Summing Point, Online, Overexcitation Limiting
The online, low-level OEL threshold is determined by the low-level setting
F
. When the excitation level is
below the low-level setting, no action is taken by the DECS-250. The generator is permitted to operate
indefinitely with this level of excitation. When the excitation level exceeds the low-level setting for the
duration of the medium time setting, the DECS-250 acts to limit the excitation to the value of the low-level
setting.
The online, medium-level OEL threshold is determined by a medium level
G
and medium time
H
setting.
When the excitation level exceeds the medium level setting, the DECS-250 acts to limit the excitation to
the value of the medium-level setting. If this level of excitation persists for the duration of the high time
setting, the DECS-250 acts to limit the excitation to the value of the medium-level setting.
The online, high-level OEL threshold is determined by a high level
I
and high time
J
setting. When the
excitation level exceeds the high level setting, the DECS-250 instantaneously acts to limit the excitation to
the value of the medium-level setting.
OEL Voltage Dependency
Online OEL operation can be tailored for fault proximity by enabling
K
the OEL voltage dependency
function. If a fault is close to the generator, the OEL high-level setting is disabled (based upon the rate of
change) and switches to the medium-level setting. If a fault is away from the machine, all three (high,
medium, and low) settings remain active. In other words, if the rate of terminal voltage reduction exceeds
the OEL voltage dependency setting
L
, the high-level setting remains enabled. Otherwise, the high-level
setting is disabled.
Figure 44. OEL Configuration Settings
F
IE
L
D
C
U
R
R
E
N
T
TIME IN SECONDS
High
Current
Time
0-10sec
CONTINUOUS
P0063-10
Medium
Current
Time
0-120sec
Low
Current
Level
Medium
Current
Level
High
Current
Level
Summary of Contents for DECS-250
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Page 6: ...iv 9440300990 Rev J Revision History DECS 250 ...
Page 16: ...xiv 9440300990 Rev J Contents DECS 250 ...
Page 20: ...4 9440300990 Rev J Introduction DECS 250 ...
Page 28: ...12 9440300990 Rev J Power Stage DECS 250 ...
Page 32: ...16 9440300990 Rev J Voltage and Current Sensing DECS 250 ...
Page 40: ...24 9440300990 Rev J Synchronizer DECS 250 ...
Page 52: ...36 9440300990 Rev J Auxiliary Control DECS 250 ...
Page 56: ...40 9440300990 Rev J Contact Inputs and Outputs DECS 250 ...
Page 84: ...68 9440300990 Rev J Limiters DECS 250 ...
Page 114: ...98 9440300990 Rev J Power System Stabilizer DECS 250 Figure 96 PSS Parameter Settings ...
Page 124: ...108 9440300990 Rev J Stability Tuning DECS 250 ...
Page 126: ...110 9440300990 Rev J Mounting DECS 250 Figure 103 Overall and Projection Mounting Dimensions ...
Page 127: ...9440300990 Rev J 111 DECS 250 Mounting Figure 104 DECS 250 Escutcheon Plate Dimensions ...
Page 198: ...182 9440300990 Rev J Timekeeping DECS 250 ...
Page 210: ...194 9440300990 Rev J CAN Communication DECS 250 ...
Page 304: ...288 9440300990 Rev J Maintenance DECS 250 ...
Page 316: ...300 9440300990 Rev J Specifications DECS 250 ...
Page 334: ...318 9440300990 Rev J Analog Expansion Module DECS 250 ...
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