C.6
SEL-787 Relay Instruction Manual Date Code 20081022
SEL Communications Processors
SEL Communications Processor and Relay Architecture
Enhancing
Multidrop Networks
You can also use an SEL communications processor to enhance a multidrop
architecture similar to the one shown in Figure C.3. In this example, the SEL
communications processor enhances a system that uses the SEL-2701 with an
Ethernet HMI multidrop network. There are two Ethernet networks, the
SCADA LAN and the Engineering LAN. The SCADA LAN provides real-
time data directly to the SCADA Control Center via a protocol gateway and to
the HMI (Human Machine Interface).
Figure C.3 Enhancing Multidrop Networks With SEL Communications
Processors
In the figure, the SEL communications processor provides the following
enhancements when compared to a system that employs only the multidrop
network:
➤ Ethernet access for IEDs with serial ports
➤ Backup engineering access through the dial-in modem
➤ IRIG-B time signal distribution to all station IEDs
➤ Integration of IEDs without Ethernet
➤ Single point of access for real-time data for SCADA,
HMI, and other uses
➤ Significant cost savings by use of existing IEDs
with serial ports
SEL Communications
Processor Example
This example demonstrates the data and control points available in the SEL
communications processor when you connect an SEL-787. The physical
configuration used in this example is shown in Figure C.4.
SEL Communications
Processor
Modem
To SCADA Control Center,
RTU, or Protocol Gateway
To Engineering
HMI/Local
Engineering
Access
SEL-421 Relay
Hub
Hub
Ethernet IED
SCADA
Ethernet LAN
EIA-232
Engineering
Ethernet LAN
SEL-787 Relay SEL Relay Non-SEL IED
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