S3 Logic Inputs - GE 750 Instruction Manual

S3 LOGIC INPUTS

5.4 S3 Logic Inputs
5.4.1 Overview
5 - 26
The 750/760 relay has twenty (20) logic inputs which can be used to operate a variety of
logic functions for circuit breaker 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 relay has 14 rear terminal contact inputs. These contacts can be either wet or dry (see
Logic Inputs on page 3–17 for typical wiring of the logic input contacts). External contacts
are either open or closed and are de-bounced for one power frequency cycle to prevent
false operation from induced voltage. Because of debouncing, momentary contacts must
have a minimum dwell time greater than one power frequency cycle.
The relay also has twenty (20) virtual inputs which are analogous to software switches.
They allow all the functionality of logic inputs to be invoked via serial communications or
from the front panel. This has the following advantages over contact inputs only:
• The number of logic inputs can be increased without introducing additional
hardware.
• Logic functions can be invoked from a remote location over a single RS485
communications channel.
• The same logic function can be invoked both locally via contact input or front
panel keypad, and/or remotely via communications.
• Panel switches can be replaced entirely by virtual switches to save cost and wiring.
Virtual inputs are simply memory locations in the relay which can be assigned a value via
communications or from the
value stored in memory is "0", then the virtual input is Off; otherwise, the virtual input is On.
The state of virtual inputs is written as if it were a setpoint; these values are non-volatile
and are found in memory map locations 0090 to 00A4 hex. Momentary virtual inputs are
simulated by first writing a "1" to the corresponding register followed by writing a "0". Due
to communications delay there will be a dwell time of 50 to 200 ms. Maintained virtual
inputs are simulated by writing a "1" to the corresponding register.
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A1 STATUS VIRTUAL INPUTS
750 FEEDER MANAGEMENT RELAY – INSTRUCTION MANUAL
CHAPTER 5: SETPOINTS
actual values menu. If the