Power over Ethernet -
The Last Frontier in Industrial Communication Standards
(from the website PowerOverEthernet.com, May 26, 2006)
Perhaps the final frontier in the
battle for dominance in industrial communications between
field buses and Ethernet, is the ability to transmit power
and data across the same wire. Shared use of cabling reduces
costs, and in some applications, is the only viable solution
for extending power to the very edge of an industrial
operation.
In the past, field buses were the only power-and-data
option. Now, IEEE 802.3af (Power overEthernet) provides
that same combined capability, and vendors are
increasing the number of industrial PoE-capable devices
available for deployment almost daily. While the
available power in a PoE-connected device is limited to
about 13 watts, the vast majority of modern industrial
sensors take 5 to 10 watts. It may soon be possible to
power a full SCADA system from ports on Ethernet
switches, along with non-traditional SCADA devices such
as IP phones, security scanners, PA systems, video
surveillance cameras and PCs.
GarrettCom, Inc., a leader in the industrial Ethernet
market, introduced what it believes to be the first
hardened PoE switch (Power Sourcing Equipment or PSE)
for industrial applications roughly a year ago, helping
to create a market for industrial PoE Powered Devices (PDs).
Just recently, GarrettCom added new flexibility to the
PoE market, by adding PoE capability to its configurable
Magnum 6K-Series hardened managed switches. Now it is
possible to integrate up to eight PoE ports in a larger
Ethernet switch, providing the convenience of a single
point of management with the flexibility necessary to
add PDs as required.
Background
Communications is the beating heart of modern industrial
SCADA applications. The ability to transfer data from
sensors, monitors and controllers to other devices
and/or to a communications center is what allows
factories, utility substations, mines, and other
manufacturing and processing facilities to achieve high
levels of efficiency and reliability.
Modern industrial data communications began with modems
and serial interfaces, the most successful being the
Field Bus. While commercial communications were evolving
to standardized vendor-independent protocols (of which
Ethernet emerged the leader), serial field buses, with
their slight-to-significant differences that often
dictated single-vendor lock-in, held sway in the
manufacturing arena because of their predictability,
their ability to run power and data across the same
lines, and their sheer volume of installations.
Over the last 5 years, industrial Ethernet has evolved
to meet industrial requirements with prioritization
techniques, faster fault-recovery, and the increasing
popularity of standardized solutions in both the
industrial and vendor communities. For industrial
decision makers, standards provide interoperability,
vendor independence, and forward compatibility as
applications and tools evolve. For vendors, building to
a standard allows them to build products in higher
volumes at lower cost. For both, training and
maintenance costs are reduced.
Conclusion
Although many industrial applications today do not
always require the higher bandwidth available from
Ethernet (10 Mb to 1 Gb and beyond), the ability to add
new applications and, particularly in the post 9/11
world, surveillance, has made Ethernet a dominant
technology when installing or replacing industrial
communications lines and industrial equipment. Security
devices such as video surveillance and ID card readers,
as well as VoIP and other conveniences, need bandwidth
far in excess of what is possible or affordable on
serial lines.
Ethernet provides the common protocol to drive
communications from the IT department at corporate
headquarters to the farthest field sensor. Although
within the industrial facility, various networks may be
segregated or firewalled for security, a single cabling
strategy and protocol provides savings in deployment
costs and training. Serial-to-Ethernet converters
support legacy applications while providing an easy
upgrade path to Ethernet as systems are replaced or
upgraded. The arrival of PoE wipes away the last
advantage of field buses and clears the way for Ethernet
to dominate in industrial control systems.
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