9-2 9492600990
Limiters DECS-150
Offline Operation
For offline operation, there are two levels of summing-point overexcitation limiting: High and Low. Figure
9-2 illustrates the relationship of the high-level and low-level OEL thresholds.
Figure 9-2. Summing Point, Offline, Overexcitation Limiting
The offline, high-level OEL threshold is determined by the High Level and High Time settings. When the
excitation level exceeds the High Level setting, the DECS-150 acts to limit the excitation to the value of
the High-Level setting and a High Level Timer is initiated. If this level of excitation persists until this timer
reaches the High Time setting, the DECS-150 acts to limit the excitation to the value of the Low-Level
setting. The Ambient Temperature setting on the Rated Data Settings screen determines the high-level
range.
The offline, low-level OEL threshold is determined by the Low Level setting. When the OEL becomes
inactive, the High Current Timer counts down from either the high time, if the High Current Timer has
expired, or from the amount of time spent at high level, if the High Current Timer has not expired. The
generator is permitted to operate indefinitely with this level of excitation. The Ambient Temperature
setting on the Rated Data Settings screen determines the low-level range.
Online Operation
For online operation, there are three levels of summing-point overexcitation limiting: low, medium, and
high. Figure 9-3 illustrates the relationship of the high-, medium-, and low-level OEL thresholds.
Figure 9-3. Summing Point, Online, Overexcitation Limiting
The online, high-level OEL threshold is determined by the High Level and High Time settings. When the
excitation level exceeds the High Level setting, the DECS-150 instantaneously acts to limit the excitation
to the value of the High Level setting. If this level of excitation persists for the duration of the High Time
setting, the DECS-150 acts to limit the excitation to the value of the High Level setting. The Ambient
Temperature setting on the Rated Data Settings screen determines the high-level range.
The online, medium-level OEL threshold is determined by the Medium Level and Medium Time settings.
When the excitation level exceeds the Medium Level setting for the duration of the Medium Time setting,
the DECS-150 acts to limit the excitation to the value of the Low Level setting. The Ambient Temperature
setting on the Rated Data Settings screen determines the medium-level range.
FIELD CURRENT
TIME IN SECONDS
High
Current
Time
CONTINUOUS
P0063-09
0-10sec
Low
Current
Level
High
Current
Level
FIELD CURREN
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
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