Michiel Panders, R&M General Manager Europe looks at the cabling choices for PoE.

A recent study from MarketReportsWorld predicts that the global Power Over Ethernet (PoE) Device market size will reach US$ 2.9B by 2027, from US$ 2.5B in 2020. This growth is due to the increasing penetration of IoT across industrial sectors, in commercial buildings, and at home. New PoE-capable devices for smart buildings are coming onto the market almost every day. To support a wide range of business-critical applications, all of these devices require high levels of power and connectivity.

In our daily lives, we have become highly accustomed to a wide range of USB end point accessories, which are connected and powered using different types of USB connector. Similar to this evolution of USB, we’re seeing end point devices that require a switched network connection increasingly combining Ethernet network capabilities with the power interface offered by PoE.

The higher voltage used in PoE compared to USB (48v vs 5v), allows devices to be connected over longer distances, which suits different applications. The cable type used determines the maximum current and, therefore, the maximum power level. Today, 90W per connection is possible, making PoE a viable, optimized alternative for many end point devices rather than using separate power connections that often come with external adapters. With 4PPoE, up to 90 watts of electrical power are feasible - more than three times as much as the previous standard and more than six times as much as the original PoE standard. The use of direct PoE connections not only reduces the number of required outlets, but also “adapter waste”. On top of that, power can be easily switched on or off and monitored.

The increased PoE power drives heat and connectivity considerations, adding a new dimension to the cabling infrastructure. Push in wire-connectors in 230v installations are designed to support the highest possible current, and the RJ45 connectors in a PoE enabled network require similar consideration. On top of that, vibration and patching are crucial (especially in IoT applications) for determining how wires are terminated in the connector in order to withstand these external factors and ensure the correct working and safety of the connection.

Temperature increases in the cable due to power transmission and degrading contacts in the wire termination. Cables and cable bundles heat up as a result of current supply. Material can be damaged and higher attenuation losses may affect data transmission in the LAN. Contact resistances on wire contacts may increase if the contacting surfaces become loose, age, or corrode. This also has an adverse effect on data transmission. A PoE-compliant design ensures the cabling system can withstand higher temperatures. One of the most important preventive measures is to plan shorter links, if necessary. The shorter the cable run, the smaller the attenuation losses during data transmission and the greater the reserves for heating effects.

Another important consideration is the destruction of the RJ45 contacts as a result of sparks when disconnecting under load. Spark erosion can damage spring contacts in the RJ45 adapters, and poor contacts mean poor signal transmission. Whether an RJ45 socket suffers from spark erosion depends on its mechanical construction and contact design. These characteristics should be taken into account when selecting a product and specified accordingly. The IEC 60512-99-1/2 standards are available for this purpose.

Networks are expected to remain in operation for over 15 years, so from a bandwidth as well as a power perspective it makes sense to design for what is likely to come in the next 10 years as a minimum. That’s why it is all the more important to pay attention to future power and bandwidth needs when specifying the cable and defining the right Remote Powering (RP) certification class you need your infrastructure to comply with.