7.3
Date Code 20170927 Instruction Manual SEL-751 Relay
Communications
Communications Interfaces
Fiber-Optic Serial Port
Use the optional fiber-optic port (Port 2) for safety and communications
distances as far as 1 km. For communications distances as far as 4 km, use an
SEL-2812 transceiver on Port 3. Although Port 2 and the SEL-2812 are
compatible, Port 2 is less sensitive than the SEL-2812, which limits the
distance to 1 km. This port can receive the RTD measurement information
from the optional external SEL-2600 RTD Module.
Ethernet Port
Use the Ethernet port for interfacing with an Ethernet network environment.
SEL-751 Ethernet port choices include single or dual copper or fiber-optic
configurations. With dual Ethernet ports, the unit has an unmanaged Ethernet
switch. Redundant configurations support automatic failover switching from
the primary to the backup network if the relay detects a failure in the primary
network. The basic concept in the Parallel Redundancy Protocol (PRP) mode
of operation is that the Ethernet network and all traffic are fully duplicated
with the two copies operating in parallel. The purpose of the protocol is to
provide seamless recovery from any single Ethernet network failure. In
addition to failover and PRP modes, the unit can operate in a “fixed
connection (to netport) mode” or in a “switched mode” (as an unmanaged
switch).
Figure 7.1 shows an example of a simple Ethernet network configuration,
Figure 7.2 shows an example of an Ethernet network configuration with dual
redundant connections, and Figure 7.3 shows an example of an Ethernet
network configuration with ring structure.
Figure 7.1 Simple Ethernet Network Configuration
CAT 5 shielded twisted pair (STP)
cables with RJ45 connectors
(SEL-C627/C628) for
copper Ethernet ports
OR
Fiber-optic Ethernet cables with
LC connectors (SEL-C808) for
fiber-optic Ethernet ports
Set Port 1 (Ethernet) settings in each relay.
NETWORK
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