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Electric Energy T&D - Index

Electric Energy T&D - EEMag March / April 2008 - Index

Peer-to-peer protection and control systems
implemented over Ethernet addresses the
available bandwidth problem that can
occur with peer-to-peer protocols such as
GOOSE messaging, part of the UCA .0/IEC
61850 standards.
Some relay manufacturers have developed their
own proprietary peer-to-peer communications
protocol originally designed to work over serial
networks with operating speeds as expected
for the application.
The fact that not all relay vendors choose to
follow international standards force end users
to search for ways to allow the co-existence
of serial and Ethernet systems in the same
network, eliminating the need to build and
maintain two or more separate networks.
SERIAL TO ETHERNET TECHNOLOGIES
Overview
Ethernet infrastructure is usually available,
or can be easily implemented. Buildings tend
to have existing Ethernet networks. PLC and
RTU manufacturers are starting to develop
Ethernet add-ons to network their products,
at a premium cost for this functionality.
Serial servers are a cost effective solution
that, utilizing Serial-to-Ethernet technology,
allow integrating serial devices that are not
Ethernet capable together with Ethernet
capable devices on the same local area
network (LAN).
A transparent serial tunnel is created over
Ethernet without changing much of the existing
setup. The ability to create Virtual COM Ports
eliminates the need to upgrade the existing
hardware with network add-on modules.
The main benefits of having access to the
substation LAN are:
• High-speed peer-to-peer communications
between IEDs
• Reduced inter-IED wiring
• Coexisting multiple protocols on the same
physical network
• Fast Network Recovery utilizing protection
protocols like eRSTP for more reliability
should a link failure occurs.
Over all result is a protected network
architecture that provides reliability and high
availability with all components integrated
on the same Ethernet backbone network at
lower cost.
RaW Socket TCP/IP
The basic idea behind Raw Socket is extending
a serial network behind serial communications
limitations by encapsulating serial data in IP
datagrams that can travel over a standard IP
network that spans across cities, countries,
and some times continents.
Socket mode of operation provides a way
of directly accessing device servers across
a TCP/IP network without first having to
install a driver. Sockets are standard APIs
(Application Programming Interfaces)
used to access network devices over a
TCP/IP network. Two socket API standards
are in common use. The original
standard, known simply as ‘Sockets’, was
March-April 2008 Issue I
developed for the Unix/Linux environment.
The Windows alternative is ‘Win Sock’.
Although there are fundamental differences
between these two standards, most
of the API function calls from either
system have the same structure and
consequently, socket based network control
programs are portable across almost all
system platforms.
Two appropriately configured device servers
can work in unison to form a serial tunnel.
The serial tunnel operates by encapsulating
serial data in a TCP/IP packet, which is then
transported across an Ethernet network.
This operation mode allows transparent
connection of all serial devices and is also a
good way to network DOS based PCs or PDAs,
or two serial IEDs connected in a peer-to-peer
mode using IEC61850 GOOSE messages or
SEL Mirrored Bits ® . Because the connection
is truly transparent, proprietary protocols can
be transmitted.
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