CHAPTER 8: AUTOMATION
AUTOMATION INPUTS AND OUTPUTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
465
Figure 391: Contact input and output assignments
All available contact inputs and output can be reassigned using the
>>
and
<<
buttons.
Contact input configuration
The D90
Plus
can monitor the status of up to 115 field contacts. Each input can be wetted
from the D90
Plus
48 volt auxiliary supply or from an external power supply. Each digital
input has a dedicated delay timer for filtering of contact bouncing. The D90
Plus
can also
detect an oscillating input via the chatter feature. Each contact input active impedance
circuitry to provide security against false turn-on of an input due to excessive stray
capacitance of field wiring.
A raw status is scanned synchronously for all contact inputs at the rate of 0.25 ms as
shown below. A new contact input state must be maintained for a user-programmable
debounce time for the D90
Plus
to validate the new contact state. The debounce time is set
at 2.0 ms in the figure below; as such, the eighth sample validates the change of state
(mark 1 in the figure below). Once validated (de-bounced), the automation contact input
asserts a corresponding automation operand and logs an event (if event logging is
enabled).
A time stamp of the first sample in the sequence that validates the new state is used when
logging the change of the contact input into the event recorder (mark 2 in the figure
below).