DECS-100 BESTCOMS for Windows
®
OS
5-17
Figure 5-18. Metering, Operation, and Alarms, Alarm/Status Tab
Switch Status. Three Switch Status indicators indicate when the DECS-100 control inputs are open or closed.
The 52JK switch open indicator changes from black to red when the user-supplied contacts at terminals 52J
and 52K are closed. When this control input is open, selection of PF or VAR mode can be made on the
Operation tab of the Metering, Operation, and Alarms screen. The 52LM switch closed indicator changes
from black to red when the user-supplied contacts at terminals 52L and 52M are closed. When this control
input is closed, parallel control and droop is inactive. The VM switch closed indicator changes from black to
red when the user-supplied contacts at terminals VM and VMC are closed. When this control input is closed,
the Voltage Matching function is active.
Metering Signal. The Metering Signal indicator of the Alarm/Status tab flashes to indicate when metering is
active. A number beside the indicator tracks how many times the metering and status indicators have been
updated. When the Metering button is clicked or Metering on the Menu bar is clicked followed by Disable
Metering, the Metering Signal indicator stops flashing, the metering update counter stops incrementing, and
the metering functions stop being updated.
PID DATA
BESTCOMS-DECS100-32 enables generator stability to be set through the automatic calculation of PID
parameters. PID stands for Proportional, Integral, Derivative. The word proportional means that the response
of the DECS-100 output is proportional or relative to the amount of change that is observed. Integral means
that the DECS-100 output is proportional to the amount of time that a change is observed. Integral action
eliminates offset. Derivative means that the DECS-100 output is proportional to the required rate of excitation
change. Derivative action avoids excitation overshoot.
BESTCOMS automatically calculates PID values after the user selects the generator frequency, generator
time constant (T'do), and exciter time constant (Texc). With BESTCOMS, the user may generate new PID
numbers, add to a PID list file, and update the AVR gain settings in the Control Gain or Step Response
screens.
The PID window (Figure 5-19) is accessed by clicking the PID button. The PID button can be clicked only
when the Stability Range setting of the Control Gain screen is set at a value of 21. (A setting of 21 enables
the entry of custom stability settings through the PID window.) Then, when a field of the Control Gain screen