PoE: With a Cool Head to Cool Cables

Shajan George, Sr. Director – Private Network, R&M India & SAARC

Shajan George, Sr. Director – Private Network, R&M India & SAARC

Power over Ethernet is booming. According to market studies, the number of PoE ports will double by 2027. New PoE-capable devices for LANs, industry and building automation come onto the market almost daily, which is why now in particular it is all the more important to pay attention to the right cabling. Otherwise, things could get dangerously hot. 

The demand for PoE is growing with new application possibilities – for example in smart buildings. Power supply via data cables is ideal for operating building automation devices. Today, countless terminal devices of the Internet of Things (IoT), room sensors, IP cameras and access points can be powered via PoE. Even PoE-capable, LAN-controllable LED lights (connected lighting) are becoming increasingly popular. IP-based networking in production – Industry 4.0 – also relies on PoE. New construction directives should lead to a reduction in power consumption and CO2 emissions. PoE can help to achieve the defined goals.

Four-pair PoE becomes standard

The latest PoE generation delivers power via all four twisted pairs of the data cable (4PPoE). At 90 watts, it offers more than three times as much electrical power as the previous standard – and more than six times as much as the original PoE standard. High-power PoE has considerable consequences for structured cabling. Users should keep a cool head and not plunge into PoE applications without first planning carefully. There are several criteria to be considered when selecting and handling the cabling. 

Cables can get hot

The first point: 4PPoE can heat cables. The greater the power transmitted, the more heat is generated. Several criteria must be considered in particular during network planning and installation: cable type, cable diameter, bundle size, characteristics of the cable duct and length of the connections. If you plan appropriately and choose suitable products, your cabling system will be able to withstand higher temperatures. The PoE Calculator helps one to find the right solution. One of the most important preventive measures is to plan shorter links. The shorter the cable link, the less resistance, heating and attenuation losses during data transmission.

Take spark erosion into account

The second point: connectors. When a connection is cut under load, sparks are generated. Spark erosion can damage the spring contacts in the adapters. The greater the power transmitted, the greater the risk. Whether an RJ45 jack is affected depends on its mechanical construction and the contact design. These characteristics should be taken into account when selecting a product and specified accordingly. 

Consider the connection technique

– The insulation piercing contact, IPC, which is frequently used in patch cords, is unstable over the long term. The connection may become loose if the material ages or as a result of cable movements. The contact resistance between the contact mandrel and the stranded wire increases and with it the danger of heat developing and contact loss in the connector.

– Insulation Displacement Contact (IDC) ensures consistently high contact quality over the entire service life of the product. In IDC, a fork-shaped spring contact clamps the wire. The contacts cut through the insulation and press the stranded wire at the side. This makes the connection permanently resistant to tension and vibration, dust-tight, water- and gas-tight, and corrosion-free. Recommendation from R&M: IDC should be chosen for channels with continuous, high PoE performance and the use of 4PPoE. Patch cords with IDC termination ensure reliable long-term connection security.

Standardization has responded

The international standard-setting bodies have recognized how important the topic of PoE has now become. The cabling installation standards (ISO/IEC 14763-2 and EN 50174-2) have been expanded by the remote power supply categories RP1 – RP3. The various categories define what is necessary before installation and during operation to be able to operate cabling safely with PoE. Operators of cabling installations will have to consider how to operate PoE in their own buildings. 

Three ‘hot’ factors influence cabling with 4PPoE: Heating of cable bundles due to current carrying, spark erosion when unplugging, and contact resistance at the wire contact. Using the PoE Calculator and the PoE-optimized connectivity technology users can set up the infrastructure for safe high-power applications with long-term stability.

The above article is authored by Shajan George, Sr. Director – Private Network, R&M India & SAARC

Leave a Reply