CHAPTER 2: INSTALLATION ELECTRICAL INSTALLATION
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL 2–33
Contact Inputs
Depending on the order code, the 850 relay has a different number of contact inputs which
can be used to operate a variety of logic functions for circuit switching device control,
external trips, blocking of protection elements, etc. The relay has ‘contact inputs’ and
‘virtual inputs’ that are combined in a form of programmable logic to facilitate the
implementation of various schemes.
The voltage threshold at which the contact inputs detect a closed contact input is
programmable as 17 V DC for 24 V sources, 33 V DC for 48 V sources, 84 V DC for 110 to
125 V sources, and 166 V DC for 250 V sources.
Wet or Dry input signal types can be connected to contact input terminals as shown in the
figure: Wet and Dry Contact Input Wiring Examples.
Dry inputs use an internal +24V that is supplied by the 850. The voltage threshold must be
set to 17V for the inputs to be recognized using the internal +24V.
FAST PATH:
The same type of input signal must be connected to all contact inputs on the same contact
input card.
Figure 2-37: Wet and Dry Contact Input Wiring Examples
INPUT
SIGNAL
SWITCH
(DRY)
INPUT
SIGNAL
SWITCH
(WET)
EXTERNAL
DC POWER
SUPPLY
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