9440300990 Rev J
41
DECS-250
Protection
Protection
The DECS-250 offers protection relating to generator voltage, frequency, power, field parameters, rotating
exciter diodes, power input failure, and generator-to-bus synchronism. Configurable protection elements
supplement this protection with additional, user-defined system parameters that have multiple pickup
thresholds per parameter. Most protection functions have two groups of settings labeled Primary and
Secondary. Two setting groups enable independent protection coordination which is selectable in
BESTlogic™
Plus
.
Voltage Protection
BESTCOMSPlus Navigation Path:
Settings Explorer, Protection, Voltage
HMI Navigation Path:
Settings, Protection, Voltage Protection
Voltage protection includes overexcitation, generator undervoltage, generator overvoltage, and loss of
sensing voltage.
Overexcitation (Volts per Hertz)
Volts per hertz protection is annunciated if the ratio of the per-unit voltage to the per-unit frequency
(volts/hertz) exceeds one of the Volts per Hertz Pickup Level
A
settings for a definite amount of time
B
. If the
Volts per Hertz Pickup level is exceeded, timing will continue until the volts per hertz ratio drops below the
dropout ratio (95%). Volts per hertz protection also guards against other potentially damaging system
conditions such as a change in system voltage and reduced frequency conditions that can exceed the
system’s excitation capability.
Several volts per hertz settings enable the DECS-250 to provide flexible generator and generator step-up
transformer overexcitation protection. An inverse square timing characteristic is provided through the
Inverse Time Pickup Setpoint
C
and Time Dial
D
settings. These settings enable the DECS-250 to
approximate the heating characteristic of the generator and generator step-up transformer during
overexcitation. A linear reset characteristic is provided through the Reset Dial
E
setting. Volts per hertz
protection can be enabled and disabled
F
without altering the pickup and time delay settings.
Two sets of fixed-time, overexcitation pickup settings are available through the Definite Time Pickup #1,
#2 and Definite Time Delay #1, #2 settings.
The following equations represent the trip time and reset time for a constant V/Hz level. Volts per hertz
characteristic curves are illustrated in Figure 25 and Figure 26.
n
NOMINAL
MEASURED
T
T
Hz
V
Hz
V
D
T
−
=
1
/
/
100
×
×
=
FST
E
D
T
T
R
R
Equation 7. Trip Time
Equation 8. Reset Time
Where:
T
T
= time to trip
T
R
= time to reset
D
T
= time dial trip
D
R
= time dial, reset
E
T
= elapsed time
n = curve exponent (0.5, 1, 2)
G
FST = full scale trip time (T
T
)
E
T
/FST = fraction of total travel toward trip that integration had progressed to. (After a trip, this value
will be equal to 1.)
Содержание DECS-250
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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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