Section 6: Data Comms Connections; Rs485 Connection; Irig-B Connections; Optional Fibre Optic Connections - Siemens 7SR23 DAD Manual

High impedance protection relay

Section 6: Data Comms Connections

6.1

The RS485 communication port terminals are located on the rear of the relay and can be connected using a

suitable RS485 120 screened twisted pair cable.

The RS485 electrical connection can be used in a single or multi-drop configuration. When used with Reydisp the

RS485 master must support and use the Auto Device Enable (ADE) feature.

The last device in the connection must be terminated correctly in accordance with the master driving the

connection. A terminating resistor is fitted in each relay, when required this is connected in circuit using an

external wire loop between terminals 18 and 20 of the power supply module.

Up to 64 relays can be connected to the RS485 bus.

Each relay has an internal terminating resistor – this can be connected in circuit where necessary.

6.2

A BNC plug is provided to connect a co-axial cable carrying IRIG-B time synchronisation signals. Ensure that the

stub length is minimised by connecting the tee-connector directly to the rear of the relay. A suitable co-axial cable

would be type RG 58 50ohms

Where fitted rear Data Comms ports 3 and 4 comprise Fibre–Optic ST™ (BFOC/2.5) bayonet connectors-4 per

product. 62.5 / 125 m glass fibre is recommended for all lead lengths.

When installing fibre, ensure that the fibres' bend radii comply with the recommended minimum for the fibre used-

typically 50mm is acceptable.

The fibre optic data comms link will be interrupted if the relay element is withdrawn from the case.

Figure 6.1-1 RS485 Data Comms Connections

Chapter 5) 7SR23 DAD Installation Guide

Chapter 5 Page 16 of 24

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