Basler DECS-200 User Manual

DECS-200 Functional Description 3-11
When the underfrequency function is active, an
underfrequency annunciation occurs. Underfre-
quency is annunciated on the front panel Metering
screen and may be assigned to a programmable
output relay for external annunciation.
Volts per Hertz Ratio Limiter
The volts per hertz ratio limiter prevents the
regulation setpoint from exceeding the volts per
hertz ratio that is prescribed by the slope setting
of the DECS-200 as stated in the previous
paragraphs. This feature is also useful for other
potentially damaging system conditions such as a
change in system voltage and reduced frequency
situations that could exceed the systems volts per
hertz ratio limit. Figure 3-5 illustrates a typical 1.10
PU volts per hertz limiter curve.
Overexcitation Limiter (OEL)
Overexcitation limiting operates in all modes
except FCR mode. The DECS-200 senses the
field current output and limits the field current to
prevent field overheating. In FCR mode, the
DECS-200 announces that all conditions for OEL
are fulfilled. The DECS-200 provides two types of
overexcitation limiting: Summing Point and
Takeover.
Summing Point OEL
Two OEL current levels are defined for off-line
operation: high and low (see Figure 3-6). The
generator can operate continuously at the low
OEL current level and for a programmed time at
the high OEL current level.
V
ol
t
s
/
H
er
t
z
R
at
i
o
GENERATOR VOLTS
GENERATOR FREQUENCY
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0 %
110 %
Nominal
0 Hz
100 %
Figure 3-5. Typical 1.10 PU V/Hz Limiter Curve
FIELD CURRENT
TIME IN SECONDS
High
Current
Time
CONTINUOUS
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0-10sec
Low
Current
Level
0-15Adc
High
Current
Level
0-30Adc
Figure 3-6. Off-Line Overexcitation Limiting
Three OEL current levels are defined for on-line operation: high, medium, and low (see Figure 3-7). The
high and medium current levels can be maintained only for a user-defined amount of time. The generator
can operate continuously at the low OEL current level.
FIELD CURRENT
TIME IN SECONDS
High
Current
Time
0-10sec
CONTINUOUS
D2851-17.vsd
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Medium
Current
Time
0-120sec
Low
Current
Level
0.0 - 15 Adc
Medium
Current
Level
0.0 - 20 Adc
High
Current
Level
0.0 - 30Adc
Figure 3-7. On-Line Overexcitation Limiting
The 52L/M (unit/parallel) contact input status determines which limiter is active (on-line or off-line). When
the 52L/M input is closed, the off-line limiter is active. When the 52L/M input is open, the on-Line limiter
setting is active.

Basler DECS-200 Specifications

General

Brand	Basler
Model	DECS-200
Category	Controller
Language	English