Installation guide

Network Infrastructure for EtherNet/IP™
Planning the Infrastructure
3-17
3.3 Ethernet Cabling Systems
New Ethernet installations are based on twisted-pair and fiber-optic cables. The following presents
general guidelines and an overview of cabling schemes. The use of industrial grade Ethernet cable is
critical for withstanding exposure to harsh environments.
3.3.1 Star Topology: The Standard Approach
Industrial Ethernet systems are laid out in a point-to-point cabling scheme with one cable used for each
device being connected. These individual connections are coordinated through an Ethernet switch in a
cabling topology known as a
star configuration.
The star configuration simplifies troubleshooting for device, cable, and connection installation problems.
With this star approach, multiple infrastructure components are interconnected, and each infrastructure
component connects in a star fashion to a group of individual control devices. This approach provides a
flexible, distributed control architecture.
Most manufacturers offer pre-made or custom “patch” cables in a wide variety of lengths. Typically a
backbone of switches will be connected with copper cables up to 100 meters (328 ft) in length or longer
fiber-optic cables, where each switch isolates a machine or major part of a machine. The other ports of the
switch connect to the control devices using twisted-pair or fiber cables for that part of the machine or
manufacturing process.
In a situation where there are more devices than switch ports to accommodate them, connecting one of the
first switch’s ports over to a port on a second switch effectively adds more ports to the first switch. Some
active infrastructure components have a modular hardware-expansion capability where additional ports
may be added (without using a device connection port) by plugging together port expansion modules.
Another option is to select a switch with additional ports and use the smaller switch elsewhere. It is often
wise to choose a larger switch than necessary and leave a few open ports. This way, when it comes time
to add sensors, actuators or subnetworks, it will not be necessary to replace the switch.
3.3.2 Implementation of Mixed Cable Systems
Infrastructure components, such as media converters, allow copper wire (twisted-pair) and fiber-optic
cables to be mixed in the same system. Industrial Ethernet systems may require the use of fiber optics to
cover the longer cable-run distances that would previously be implemented with copper wire at lower
data-rate settings in device-level networks. Also, the added noise immunity of fiber, especially at the 100-
Mbps and 1-Gbps rates, can reduce start-up surprises. This is especially true when routing wires near
welders, larger horsepower drives, motors, or motor starters.
3.3.3 Applicable IEEE Standards for Twisted-pair Ethernet
The major IEEE standards that apply to industrial twisted-pair Ethernet installations are 10 Base-T for 10-
Mbps connections and 100 Base-TX for 100-Mbps or
fast Ethernet operation. The term “fast Ethernet”
applies to the standards that support 100-Mbps operation. Gigabit Ethernet (1000 Base-T) operates at
1000 Mbps.
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3.3.3.1 Unshielded Category 5e Cable
The Unshielded Twisted Pair (UTP) wiring standard, which allows for flexibility and ease of installation
and maintenance, is the most prevalent cabling scheme in use today. There are two twisted-pair (four
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IEEE Std 802.3. http://standards.ieee.org/getieee802/portfolio.html