Fiber Optic Interface For Dnp3.0 Or Modbus Communications - Advanced Power technologies TTC-1000 Instruction & Operation Manual

For the panel configuration, there is no internal resistor. The terminating resistor
would be connected across the A and B terminals of the RS-485 connection on
TB2.
There are many good references on implementing multi-drop RS-485
communication links from the semiconductor divisions of Texas Instruments,
National Semiconductor, and MAXIM Integrated Products.
NOTE: Shielded cable is required for the RS-485 interface connection.
Ground shield only at one end. It is recommended that the shield drain is
grounded to the TTC-1000 chassis. Shielded twisted pair cable is
recommended. Not grounding the shield on the TTC-1000 end will either
result in spurious communications or possible damage to the RS-485
interface. In the event that the shield must be grounded on the opposite
end of the TTC-1000, a 300 volt, 0.47 µF capacitor should be added between
the shield drain and the TTC-1000 chassis. Alternatively, a 300 volt, 1.0 µF
capacitor can be used for every two shield drain wires.
A capacitor kit (part number 8AOMKIT0000), which includes one 300V, 1.0
µF capacitor is available from Advanced Power Technologies.

3.7.4 Fiber Optic Interface for DNP3.0 or MODBUS Communications

Both panel and NEMA units can be equipped with the optional DNP3.0 or
MODBUS communications interface using a plug-in Communications Processor
module with a multi-mode fiber optic interface. The module contains a separate
microprocessor to handle all overhead functions associated with the DNP3.0 or
MODBUS protocol without affecting operation of the transformer cooling control
and monitoring. Fiber optics are recommended for substation installations as it
avoids the problems of ground potential rise issues commonly associated with
direct metallic connection.
The optical interface operates at a wavelength of 850nm with 50 or 62.5 micron
multi-mode fiber terminated with either ST style connectors or V-Pin style
connectors. As with all fiber optic communication links, the optical budget is an
important number in determining the maximum distance that can be spanned
with a specific manufacturer's fiber. All optical fiber, whether it is glass or plastic
core, has a specific loss in dB per kilometer. It is important to remember that
optical losses can vary from manufacturer to manufacturer for the same core
diameter and material. The maximum distance which can be spanned is defined
by the following equation:
DISTANCE in km = (Optical Budget – 3dB) / Optical Loss in dB/km
ST Style Optical Budget Specifications:
25 V6.70 20131017