PRS-7910
PRS-7910 23
9 Communication
9.1 Overview
This section outlines the remote communications interfaces of CYG SUNRI Relays. The protective
device supports a choice of three protocols via the rear communication interface (RS-485 or
Ethernet), selected via the model number by setting. The protocol provided by the protective
device is indicated in the menu “Settings→Device Setup→Comm Settings”.
The rear EIA RS-485 interface is isolated and is suitable for permanent connection of whichever
protocol is selected. The advantage of this type of connection is that up to 32 protective devices
can be “daisy chained” together using a simple twisted pair electrical connection.
It should be noted that the descriptions contained within this section do not aim to fully detail the
protocol itself. The relevant documentation for the protocol should be referred to for this
information. This section serves to describe the specific implementation of the protocol in the relay.
9.2 Rear Communication Port Information
9.2.1 RS-485 Interface
This protective device provides two rear RS-485 communication ports, and each port has three
terminals in the 12-terminal screw connector located on the back of the relay and each port has a
ground terminal for the earth shield of the communication cable. The rear ports provide RS-485
serial data communication and are intended for use with a permanently wired connection to a
remote control center.
9.2.1.1 EIA RS-485 Standardized Bus
The EIA RS-485 two-wire connection provides a half-duplex fully isolated serial connection to the
product. The connection is polarized and whilst the product’s connection diagrams indicate the
polarization of the connection terminals it should be borne in mind that there is no agreed
definition of which terminal is which. If the master is unable to communicate with the product, and
the communication parameters match, then it is possible that the two-wire connection is reversed.
9.2.1.2 Bus Termination
The EIA RS-485 bus must have 120Ω (Ohm) ½ Watt terminating resistors fitted at either end
across the signal wires. Some devices may be able to provide the bus terminating resistors by
different connection or configuration arrangements, in which case separate external components
will not be required. However, this product does not provide such a facility, so if it is located at the
bus terminus then an external termination resistor will be required.
To Next Page
Loading...
Need help?
General