C.5
Date Code 20170927 Instruction Manual SEL-751 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 that integrate, automate, and improve station operation.
Most system integration architectures utilizing SEL communications processors
involve either developing a star network or enhancing a multidrop network.
Developing
Star Networks
The simplest architecture using both the SEL-751 and an SEL
communications processor is shown in Figure C.1. In this architecture, the
SEL communications processor collects data from the SEL-751 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 has a shorter lag time (data latency); communications overhead is much
less for a single data exchange conversation to collect all substation data (from
a communications processor) than for many conversations necessary 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
and eliminating redundant communications 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-751 Relays and other serial IEDs. The
SEL-751 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 accommodates
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.
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. In the example, 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).
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