1.Optical Communication Port On The Rear Panel; 2.Isolated Rs-485 Connection On The Rear Panel - ABB REX 521 Technical Reference Manual, General

REX 521
4.1.12.1.
4.1.12.2.
32
Protection Relay
Technical Reference Manual, General
Optical communication port on the rear panel
The fibre-optic interface on the rear panel contains two optical connectors, Tx
(X3.2) and Rx (X3.3). The connectors are used for interfacing the unit to an optical
fibre bus using either plastic fibre or glass fibre cables. See also Figure 4.1.12.5.-2
on page 35 for more information about the plastic and glass fibre cables.
The incoming optical fibre is connected to the receiver, input Rx, and the outgoing
optical fibre to the transmitter, output Tx. Special attention should be paid when
handling, mounting, and connecting fibre-optic cables. For additional information,
see the document 34 SPA 13 EN1
instructions for mounting
The communication port supports five different protocols, SPA, LON,
IEC 60870-5-103, Modbus and DNP 3.0. The SPA, IEC_103, Modbus and DNP 3.0
protocols are always supported while LON is not available in all the relay variants.
The relay does not automatically recognize which bus it is connected to and
therefore the protocol must be set manually through the HMI or the Relay Setting
Tool
(Main menu\Configuration\Communication\Rear port). For rear
port options, see Table 4.1.12.2-1.
Isolated RS-485 connection on the rear panel
The RS-485 port is used for connecting the unit to the communication bus by using
twisted pair cable. When the shielded twisted pair cable is used (recommended), the
shield can be connected to the earthing connector which is located on the rear panel
(see "Terminal connections" on page 53).
The communication port can be used with three different protocols: SPA, Modbus
and DNP 3.0. The user must set the selected protocol manually by using the HMI or
the Relay Setting Tool (Main
menu\Configuration\Communication\Rear port). For options, see
the table Table 4.1.12.2-1.
Table 4.1.12.2-1 Rear port options
Option
SPA
LON
IEC_103
Modbus
SPA - RS485
Modbus - RS485
DNP 3.0 - RS485
DNP 3.0
Plastic-core fibre-optic cables. Features and
.
Rear port
optical
optical
optical
optical
RS-485
RS-485
RS-485
optical
1MRS 751108-MUM