This standard promises to open up new possibilities for the application of this technology, but network planners must be aware of the consequences and risks of passing more electrical power through data network cabling. To provide them with all the relevant information, Reichle & De-Massari has published a new technical report on its website addressing these issues.
Power over Ethernet (PoE), the combination of power and data transmission over a single LAN cable, is becoming an increasingly popular technology. Sales of PoE-enabled devices, such as webcams, WLAN antennas, IP phones, and many other peripherals, are growing at an annual rate of over 20 percent.
PoE eliminates the need for power outlets when installing these peripherals, as a separate power source is not required, and avoids the need for additional cabling. It reduces installation costs and time, and ensures 24/7 device operation even during a power outage. This is a crucial aspect for large-scale installations, such as
building security and control systems.
The IEEE 802.3af standard for conventional PoE allows for a power supply of up to 12.95 W, but the new IEEE 802.3at standard for PoE Plus is expected to be published in 2009. This new standard will allow for a power supply of 24 W, almost double the current amount. The potential applications multiply if higher power levels can be delivered using PoE Plus. In the long term, the goal is to be able to power devices such as high-performance antennas, videoconferencing equipment, security systems, flat-panel displays, and even computers via the LAN connector.
However, R&M has produced a technical report for network planners, warning of the consequences and risks associated with PoE+. First, it states that the more electrical power is fed into the data cable, the more heat is generated. This could jeopardize the continued operational safety of the network. While the company acknowledges that "the heating issue can be controlled if the standard is applied consistently," it also points out that under certain conditions, such as areas with high ambient temperatures, specific limitations may apply, and
shorter cable runs may be necessary.
Another risk is the degradation of the contact point, as sparks can fly when live connectors are unplugged, potentially damaging the contact surfaces. This aspect was not addressed during the standardization process for PoE+, and R&M cautions: "Because of these unresolved issues, it would be premature to offer guarantees of proper functioning for any cabling system operating with PoE+."
Regina Good-Engelhardt, Product Manager at R&M, explains: “Research conducted by R&M indicates that the quality of connector contacts can be maintained through high-level solutions. Crucial factors include the characteristics of the contact material, the contact coating, and the shape and strength of the contact.”
