Communication between PLC and Digital relays in Switchgear

C

Thread Starter

charzree

Dear All,

1. We have number of protective relays in our switchgear to be connected to PLC. These relays have RS-485(3 terminals), Ethernet port (RJ 45 connector) and RS-232 for communication.

Which mode of communication is reliable? The distance between switchgear and PLC panel is about 25 meters.

The PLC is Schneider M340.

2. We have a pulse output from a flowmeter (Krohne Optisonic 6300), the test certificate tells the pulse output is passive. What is the meaning of passive here? Any power supply to be given?

Thank you beforehand for any inputs.
 
Hi there,

> 1. We have number of protective relays in our switchgear to be connected to
> PLC. These relays have RS-485(3 terminals), Ethernet port (RJ 45 connector)
> and RS-232 for communication.

Any of those ports could be reliable. Ethernet is usually a good choice because of the speed but it can depend o the application. What protocols are available on the protective relay end and what protocols are available on the PLC end? Modbus RTU? Modbus TCP/IP? DNP?

Stephen
 
B
Use Ethernet. M340 supports both Modbus TCP and EtherNetIP. Ethernet is used by Schneider in their MCC switchgear and by many end users, large and small. Some MCC suppliers build switches into switchgear sections.

If you want RS458, for some reason, use the Schneider ETG100 Ethernet to Serial converter. Program using READREG and WRITEREG functions.
 
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