The extent to which PoE is used depends primarily on the range of PoE-capable devices: "In the past, PoE was retrofitted using midspan technology when required," reports Schmidt. However, this required a lot of explanation and was therefore time-consuming. "Today, users prefer to use plug-and-play solutions. Thanks to the advancing standardization and the wide range of PoE-capable switches and devices, this is also possible without any problems." Industrial switches are increasingly being equipped with PoE-capable ports, and the range of PoE-capable devices in the industry is constantly growing. "Previously, these were access points, process cameras or intelligent network nodes, for example. Now sensors and actuators that make use of remote powering are increasingly being added," says Rainer Schmidt, outlining the current development.

Great opportunities for building automation

But how far away is Power over Ethernet from standardized 100 W transmission? And which devices and applications actually need this increase in performance?

Power over Ethernet, Part 2

Today, PoE can deliver outputs of 15 W, 25 W and in future 55 W, the details of which can always be found in the device descriptions.

The transmission of 90 to 100 W, in which all four wire pairs of a data line are used for transmission, is technically feasible, which has been proven beyond doubt by studies on connectors and cables, for example. Supplying terminal devices with such a high power requirement is therefore possible, but is not necessarily the focus of technical development!

Rainer Schmidt is Chairman ISO/IEC JTC 1/SC 25 and Business Development Manager for Industrial Cabling at Harting.

© Harting

"The discussion is strongly influenced by considerations regarding the extended use of structured building cabling - in accordance with ISO/IEC 11801 or EN 50173," explains Schmidt. It is therefore less about covering the increased power requirements of end devices, such as a laptop, and more about supplying additional services with energy, such as in building automation. "Entire industries based around LED technology are currently thinking about how lighting can be used more intelligently and at the same time save energy in buildings," says Schmidt. "So if a 60 W light source is replaced by a 7 W LED with integrated hotspot function in the future, why use kilometers of heavy 230 V cables when structured building cabling can do the same?" Power over Ethernet can lead to new concepts here.

Standardization

International standardization is a prerequisite for the spread of the next generation of Power over Ethernet. This is currently in the hands of the IEEE, which will lay the foundations in cooperation with the ISO/IEC cabling standards. The IEEE is bundling the activities for the new 90 and 100 W Power-over-Ethernet in the IEEE 802.3bt working group. The standard is expected to be adopted as early as 2017. ISO/IEC is supporting the introduction of higher power levels using PoE via structured cabling by checking the compatibility of simultaneous data and energy transmission, including with regard to cable heating.

Cable manufacturers are also explicitly pointing out the higher requirements placed on components by the more powerful Power over Ethernet.

Power over Ethernet, Part 3

Leoni, for example, is working intensively on the next PoE generations - because the expectations of the technology are also high here. "Against the backdrop of the Industry 4.0 and IoT megatrends, the standardization project for single-pair shielded data cables that can transmit 1 Gbit/s over a length of up to 40 m is currently underway. This smart technology is further enhanced by the possibility of also being able to transmit energy. A mega market is on the horizon," says Yvan Engels, responsible for Market Development at Leoni. In his view, this is another reason why the trend towards PoE will continue to grow.

Critical cable heating

Although data cabling was not originally designed for energy transmission, it can be used for two purposes if the right components are selected and defined framework conditions are taken into account. In the case of cables, this means that particular attention must be paid to cable heating, which can impair the quality of data transmission and the service life of the cables, e.g. in cable bundles where there is hardly any exchange with the ambient air. Carsten Giesen from Leoni advises using shielded cables with the highest possible category (e.g. Cat. 7A), selecting large conductor cross-sections (e.g. AWG 22) or, if necessary, using special designs with permissible operating temperatures of more than 60 °C.

Matthias Gerber is Market Manager LAN Cabling at Reichle + De-Massari.

© Reichle + De-Massari

"The quality of the cabling plays a major role because otherwise performance losses can occur," confirms Rolf-Dieter Sommer, Product Manager for the Hirschmann portfolio at Belden. Network specialist R&M has developed an online calculator specifically for Power over Ethernet. The tool, which is available on the R&M website, allows users to calculate the expected temperatures in a cable bundle - and thus also determine the maximum length of a cabling route.

"There is currently a great need for information in connection with Power over Ethernet," observes Matthias Gerber, Market Manager LAN Cabling at Reichle + De-Massari. "Our PoE explanatory video is one of our most downloaded videos on YouTube."

But there is also a need for information about the connectors used.

Power over Ethernet, Part 4

This is what damaged contacts can look like, caused by so-called "tear-off sparks".

© Telegärtner

Damage to the contacts

For example, breakaway sparks may occur in future Power over Ethernet applications if a connection is disconnected during operation. "The energy of the sparks is sufficient to irreparably damage the fine contacts of RJ45 sockets and plugs, unless the products are designed for such applications," points out Dirk Traeger, Technical Solutions Manager DataVoice at Telegärtner. And this is no small problem: many product solutions - especially inexpensive ones - are offered as PoE-compatible, but only function within the narrow limits of their intended use. If the user makes a "mistake", this can lead to damage and failures. Telegärtner's connectors are designed in such a way that the area in which breakaway sparks can occur is physically separated from the area used for data transmission. This ensures that the connector offers full performance, even after accidental disconnection under load.