|
Catch Some Rays
Connecting control and monitoring systems of the modern solar network
By Bruce Hofmann, Weidmuller North America
Today’s engineers
have many options in automation control protocols, including Modbus,
DeviceNet, Profibus, CANopen, and Ethernet. The predominant control
protocol today for solar information control is either Ethernet or
EthernetIP. This is primarily due to its ease of use and open
architecture. However, even with these advantages, Industrial Ethernet
networks can be challenging to design and implement.
These challenges center around a combination of environmental and
physical factors, including temperature extremes, wind, dust, UV rays,
and industrial machinery. In addition to these factors, large distances
are usually the reality across solar collectors, buildings, and control
centers. These areas can reach into several square miles in large
applications.
Solar installations have the potential to have hundreds or thousands of
solar collectors, each with several different analog or digital I/O
points, all being connected to the industrial Ethernet network. Also,
these networks can be geographically large and cover several square
miles, with the greatest majority of the plant being located outdoors.
Based on the potential large network size and environmental conditions,
engineering and implementing a robust and reliable network is a
challenging task.
As with any system, the network is only as good as its weakest link. In
the case of an industrial Ethernet network, its weakest connection
points are often the physical layer, comprised of networking devices,
cabling, and connectors. Therefore, best practices dictate that an
industrial network should be designed with quality materials and
components.
Today’s engineers have the advantage of access to additional technology
to make large and complicated Ethernet-based networks a reality. This
new technology can be categorized into wired and wireless solutions.
Wired Solutions
Many
manufacturers offer a line of industrial Ethernet switches in both
unmanaged and managed varieties, providing engineers with a wide variety
of choices. These include unmanaged switches that either consolidate or
disseminate Ethernet traffic, to managed switches which provide many
software-based features. Typical features of a managed switch include
the ability to prioritize resources (quality of service), combine ports
for additional redundancy or throughput (port trunking), virtual private
network control (VPN), and network self-healing features. Weidmuller’s
RapidRing technology allows the switch to automatically re-route
Ethernet traffic if a loss of connection is detected, almost
instantaneously.
Switches can vary in port types and quantity, ranging from three RJ45
ports up to 24 RJ45 ports. Single- and multiple-fiber optic port models
are common, and can support single and multimode fiber types.
Engineers have to
consider extreme environmental conditions in the design of networks for
solar applications. Ethernet switches that can function underwater, or
in dirt and dust, are a necessary requirement. These switches have
additional ratings, such as IP67, that identify their ability to
maintain connections and functionality under difficult environmental
conditions. These switches have sealed ports and connectors. They can be
installed without an enclosure, and can operate in areas of extreme
temperature conditions or in dusty or wet locations—even underwater.
All this talk about
ports makes one realize that with many ports comes many cables, and
therefore, many, many connectors. This is an often overlooked area of a
network and it’s where the greatest majority of failures occur. Matching
industrial connectors and cables with industrial devices, such as
Ethernet switches, is the best way to ensure a solid and robust network.
Based on this, an entire line of industrial cables has been designed
based on the physical demands and needs of solar array system control
and monitoring.
This connection line includes copper network cables in several ratings,
including Cat5e, Cat6, Cat7, and fiber optic cables terminated with
either SC or ST connectors. All with molded connectors and shielding for
protection against ground loops and electromagnetic noise. The line also
has specialized jacketing than can survive extreme environmental
conditions, such as wide temperature extremes (-40°C to 75°C), and
tolerate the rigorous movement from high vibration if used near
machinery or motors.
High flexibility cabling is designed to minimize the affects of flexing
that can occur when used as a control cable on an adjustable solar
collector.
Keep in mind that the
switches used in a solar array system or networks are usually mounted on
DIN rails located within an enclosure of some type. Therefore, all of
the cables mentioned above need to have access, into and out of these
numerous enclosures, which are usually located across a wide geographic
area of solar collectors.
Since solar arrays are installed outdoors, thru-panel connectors need to
be designed for optimum performance against the elements. They also need
to be flexible, as the types of connections into and out of a panel or
enclosure can vary between RJ45 and fiber optic. To solve this problem,
Weidmuller has developed the STEADYTec line of industrial Ethernet
connectors. These connectors support both RJ45 and fiber optic
connectors, with three configurations. The configuration types are
Variant 1 (bayonet), Variant 4 (push-pull), and Variant 5 (heavy duty).
Durability is the top strength of the STEADYtec connector. The entire
line is UV-resistant and rated to IP67 for ingress, creating connectors
that are water-resistant, and shock and vibration tested and rated.
However, with all of this strength comes great ease of use. The entire
line is interchangeable and modular. STEADYTec connectors are designed
to withstand the demands of outdoor and industrial applications. For
example, all bulkhead connectors can receive fiber optic or RJ45
connectors, and the matching plugs can accept fiber optic or RJ45
connectors. So, no matter what type of connector style is used (bayonet,
push-pull, or heavy duty), copper (RJ45) or fiber optic connectors or
cables are possible. The illustration below displays the versatility of
this connector.
Wireless Solutions
As
discussed in the introduction, solar array systems can cover a large
geographic area, often measured in square miles. This can create
problems with Ethernet, as it can only travel 100 meters via standard
network cables (i.e. Cat5e). This limitation is overcome with the use of
fiber optic cable. With fiber optic cables, network connections can span
20 kilometers. Installing fiber optic cables throughout a campus of
solar collectors can be a very expensive operation. Some of the costs
for fiber optic networks include the fiber optic cabling, connectors,
and having the cables terminated (i.e. fusion spliced). In addition to
the direct cost of the cables, each cable needs protection from the
elements and vehicle traffic.
One cost-effective way of providing network coverage over large
geographic areas is with the use of wireless Ethernet. Weidmuller offers
the solar industry two wireless Ethernet options. A WiFi or 802.11a,b,g
2.4Ghz modem and a 900Mhz modem. These devises have an impressive
broadcast range. The WiFi (2.4Ghz) uses 400mW of broadcast power to
effectively transmit and receive information up to three miles. The
900Mhz version has a full 1watt of broadcast power, and by using the
smaller 900Mhz band, can effectively transmit and receive Ethernet data
up to 26 miles.
Each of these devices function the same way, with the largest difference
being in the frequency in which they operate. Unlike other devices on
the market today, these units offer several powerful features designed
to address the demands of the solar industry. Some of these features are
WPA2 and AES encryption, spanning tree functionality for network self
healing, and wireless signal meshing capabilities. Also, each unit can
operate as a bridge, router, access point, or client, so no matter where
in your network you need wireless access, one unit will work.
There are many types
of devices and connection points in a modern Ethernet control system.
Any one of these connections can represent a point of failure on the
network and result in a loss of control. The good news for engineers is
the availability of a range of technology options. These include either
wired or wireless, or a combination of both, and provide engineers and
system integrators with the flexibility and technology to keep even the
most demanding industrial networks stable and responsive.
Bruce Hofmann is the director of marketing for Weidmuller North America.
For additional information, visit
www.weidmuller.com. |
