Power over Ethernet (PoE)—a technology that allows network operators to provide electric power to many types of devices through the same cable as data is transmitted—has become fairly commonplace in office IT environments. Unfortunately, industrial OT environments have not yet embraced it to the same extent. And that’s a shame, because the benefits of PoE may carry even greater weight on the plant floor. However, PoE in OT areas also carries some additional challenges—challenges that your IT folks may not be aware of. Here’s how to bring the “power” of PoE to bear at your facility—while maintaining optimum reliability in both data transfer and power flow.
Electricity anywhere, any time
One of the key benefits of PoE is that nearly anybody can safely establish a new power connection without the need to call in a licensed electrician. Voltage is low and there is no heavy wiring or need for an AC outlet involved. If, for example, you need to place a dozen security cameras on your plant floor—or even outdoors—in locations where there are no convenient junction boxes, the installation cost savings can easily be thousands of dollars. Further, you can be up and running in minutes.
In addition, PoE can provide equipment with an enhanced level of scalability, flexibility and mobility that is especially valuable in the production environment. For example, when new equipment is added or modified to improve workflow and there’s a new extruder or conveyer to be monitored, or a dead zone is discovered “six feet to the left,” the network-powered camera can be quickly repositioned without the need for any electrical rewiring.
Security cameras are a common PoE application in both IT and OT environments, but they are far from the only possibility that can make sense on the factory floor. Industrial control components such as equipment sensors and controllers, wireless access points, VoIP communications equipment, keyless access control systems, smart building automation like lighting controls, wall-mounted touchscreens like electronic white boards, digital signage, intruder alarms and more can often be powered by PoE. Further, since PoE is standards-based, the technology is brand agnostic, meaning that you can run devices from a multitude of different vendors on your same network, picking and choosing the best product price and fit in each case.
Avoiding common pitfalls
There are many advantages to “doubling up” on data and power transmission, making selection of PoE in many industrial applications a “no-brainer.” Specifying the proper cable, however, is not a no-brainer—it can demand significant expertise. By adding PoE to data cables, we are adding additional current to the cabling. This current combines with the resistance of the cabling and emits heat. Increase the PoE power and the current will also increase, bringing the heating effect to a point that the cabling insertion loss may approach the limits required for reliable data transmission—intermittent or permanent data signal failure caused by the higher insertion loss of cabling in the network—escalates in a PoE application compared to a straight data network. However, even the resident IT PoE expert who successfully navigated the issue in the office environment might not realize how the issue can intensify when establishing PoE in an OT environment.
The standard and specifications for PoE and avoiding the threat of insertion loss are based on a moderate ambient temperature of 68ºF/20ºC and distances of 100m, and a savvy specifier will certainly provide a reasonable amount of wiggle room to avoid potential issues. However, this wiggle room may need to be higher in production areas—often much higher. For example, bundling cables together, as is perhaps even more common on a factory floor, tends to create pools of heat around the cabling. And, even more important to note, ambient and spot temperatures in industrial environments can often be much higher than in climate controlled office environments, due in no small part to the heat thrown off by adjacent equipment. All of this needs to be taken into account when specifying cable in order to avoid data interruptions and failure that can wreak havoc on sensitive equipment. It should also be noted that some lower quality cables available in the marketplace can be minimally complaint, “just passing” the 68ºF/20ºC requirement and quickly running into insertion loss issues as temperatures rise, whereas cables from higher quality manufacturers will often provide a wider margin of protection against insertion loss.
It’s all a balancing act, taking into account such factors as the following:
- Data rate of the application
- The ambient environment
- The power demanded
- The distances spanned
Choosing the proper category cable is just the starting point—in these sensitive applications, even the quality of the copper used in the conductor, the insulation, shielding and the jacketing materials can impact ongoing performance, even in the same cable category.
In short, the demands of placing PoE cabling in an industrial environment are significantly more challenging than when installing PoE in an office environment or when placing data-only cabling in an industrial environment. With even less room for error, that makes it even more urgent to bring on a reputable, knowledgeable, high quality cable supplier when working to gain the benefits of industrial PoE in your operation. Belden has more than 100 years of proven cable manufacturing and network experience in environments and applications of all kinds. We’re here to help.
Ron joined Belden in 2016 to help define the roadmap of technology and applications in the enterprise. Prior to this, he developed cables and connectivity for Panduit and Andrew Corp. Ron Tellas is a subject-matter expert in RF design and Electromagnetic Propagation. He represents Belden in the ISO WG3 committee, TIA TR42 Premises Cabling Standards and IEEE 802.3 Ethernet Working Group. Ron is the inventor of 16 US patents. He has a Bachelor of Science degree in Electrical Engineering from Purdue University, a Master of Science degree in Electrical Engineering from Illinois Institute of Technology, and a Master of Business Administration from Purdue University.