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C.5
Date Code 20081022 Instruction Manual SEL-787 Relay
SEL Communications Processors
SEL Communications Processor and Relay Architecture
SEL Communications Processor and Relay
Architecture
You can apply SEL communications processors and SEL relays in a limitless
variety of applications to integrate, automate, and improve station operation.
Most system integration architectures using SEL communications processors
involve either developing a star network or enhancing a multidrop network.
Developing
Star Networks
The simplest architecture using both the SEL-787 and an SEL
communications processor is shown in
Figure C.1 . In this architecture, the
SEL communications processor collects data from the SEL-787 and other
station IEDs. The SEL communications processor acts as a single point of
access for local and remote data consumers (local HMI, SCADA, engineers).
The communications processor also provides a single point of access for
engineering operations including configuration and the collection of report-
based information.
By configuring a data set optimized to each data consumer, you can
significantly increase the utilization efficiency on each link. A system that
uses an SEL communications processor to provide a protocol interface to an
RTU will have a shorter lag time (data latency); communication overhead is
much less for a single data exchange conversation to collect all substation data
(from a communications processor) than for many conversations required to
collect data directly from each individual IED. You can further reduce data
latency by connecting any SEL communications processor directly to the
SCADA master thereby eliminating redundant communication processing in
the RTU.
The SEL communications processor is responsible for the protocol interface,
so you can install, test, and even upgrade the system in the future without
disturbing protective relays and other station IEDs. This insulation of the
protective devices from the communications interface assists greatly in
situations where different departments are responsible for SCADA operation,
communication, and protection.
SEL communications processors equipped with an SEL-2701 Ethernet
Processor can provide a UCA2 interface to SEL-787 relays and other serial
IEDs. The SEL-787 data appear in models in a virtual device domain. The
combination of the SEL-2701 with an SEL communications processor offers a
significant cost savings because you can use existing IEDs or purchase less
expensive IEDs. For full details on applying the SEL-2701 with an SEL
communications processor, see the SEL
-2701 Ethernet Processor Instruction
Manual .
The engineering connection can use either an Ethernet network connection
through the SEL-2701 or a serial port connection. This versatility will
accommodate the channel that is available between the station and the
engineering center. SEL software can use either a serial port connection or an
Ethernet network connection from an engineering workstation to the relays in
the field.