By Patrick McLaughlin
As other articles in this issue detail, twisted-pair copper cabling systems are becoming the transmission media for increasing amounts of direct current power. This trend has several implications, one of which is that the end-to-end cabling system must be physically capable of supporting the specified power and data throughput levels.
Many discussions on the topic of power-over-twisted-pair-cabling justifiably center on the cable’s capabilities. Nonetheless, a system’s connectivity remains crucial to successful transmission. This article will discuss some recent developments and evolution in connectivity technology that affect the installation and use of twisted-pair cabling systems as the infrastructure for both data and power transmission.
Creating an arc
In a technical paper, Siemon explains, “Unmating a jack-plug connection while transmitting PoE power (i.e. unmating under PoE load) produces an arc within the spark gap as the current transitions from flowing through conductive metal to air before becoming an open circuit. While the level of current associated with the arc poses no risk to humans, the arcing creates an electrical breakdown of gases in the surrounding environment that erodes the plated jack-plug contact surfaces at the arcing location. When spark gap erosion occurs in the area of the fully mated position on an RJ45 connector, the result is an unreliable connection due to the contact surface damage. This can cause degraded network performance and increased bit error rates.”
In the paper, titled “The effects of spark gap erosion caused by unmating under PoE load,” Siemon continued, “Some connecting hardware manufacturers have succeeded in ensuring that arc location during the unmating cycle is separate from the fully mated position. While this may hold true for jack contacts, their contact geometry does not ensure that erosion on plug contacts is also away from the fully mated position. Erosion on either the jack or plug contacts results in an unreliable connection.”
In that document and others, Siemon points out its Z-Max, Max RJ45 and TERA jacks are constructed to deliver reliable plug-jack connection “for superior support of the latest PoE applications.” The company incorporates a curved, or crowned, contact shape for its modular jacks. John Siemon, vice president of global operations and chief technology officer for Siemon, said, “Only Siemon’s patented crowned contact geometry places arcing damage to both the plug and jack contacts away from the fully mated position. This allows our customers to connect and disconnect to the latest PoE applications with zero risk over the lifetime of the system.”
The company’s jacks have been third-party tested and certified to be in compliance with IEC-60512-99-001, which specifies the maximum allowable resistance change that mated connections can exhibit when subjected to insertion and removal cycles under PoE load.
High-speed, high-power support
Leviton’s Atlas-X1 connectors are available in shielded and unshielded options. The shielded connectors support Category 5e to Category 8 specifications, and the unshielded connectors support Category 5e to Category 6A. They all feature a tool-free termination process, and all connectors across the platform, from Category 5e to Category 8, incorporate the same termination process. They also can be reterminated.
The company explained that following the launch of Atlas-X1 in early 2015, as the market looked toward new technologies and the need for a robust jack in special applications, Leviton continued to put the connector through rigorous testing.
“Atlas X-1 connectors were found to exceed current and developing performance standards for higher wattage PoE,” the company noted. “Atlas-X1 connectors outperformed standards requirements for higher temperatures, including the IEC 60512-5-2 Connectors for Electronic Equipment standard.
“Leviton found that using a solid metal body, instead of commonly used ABS plastic, creates a 53-percent improvement in heat dissipation,” it noted. “With greater heat dissipation, the connector can minimize the potential negative effect of heating on transmission performance in high-wattage PoE applications.”
The company says that in addition to minimizing temperature rise, its Atlas-X1 connectors “are designed to prevent arcing damage in the critical contact-mating zone between the plug and connector. When a patch cord is unplugged while the connection is charged under PoE loads, arcing damage can occur to the connector and plug interface … Leviton designed the geometry of the Atlas-X1 connector so that arcing occurs at an area different from the point of contact during data transmission, so any damage will not affect the electrical performance of the connectors within a channel.”
Leviton adds that its Retention Force Technology, which maintains constant contact force at the connector and plug interface, provides an additional layer of protection against PoE arcing damage by preventing inadvertent intermittent disconnects caused by vibration or operational movement of the plug in the connector and plug mating region.
Installation innovation
When Belden introduced its REVConnect connectivity system in September, the company said it “addresses a critical market need for reliable and easy terminations that support IP convergence over a range of applications, from wired LAN to wireless access points, high-definition displays, security cameras and building automation sensors.”
REVConnect uses a single termination method and a universal termination core for all Category 5e, 6 and 6A RJ45 connectors. The connector platform’s name includes the acronym REV, which stands for reliability, ease, and versatility. “Versatility is embodied by the system’s universal core,” Belden explained. “Contractors can terminate a jack or plug onto the same core interface. This means that field-terminable plugs, which support Category 6A and high PoE performance, can be terminated just as quickly and easily as a jack.”
When describing the process by which the REVConnect platform was developed, Belden explained that among the requirements was for PoE performance to reach 100W. “With today’s emerging applications and devices, achieving 100W was not just a cable-only requirement, but a system requirement. REVConnect has been tested and shown to support 100W devices, such as LCD monitors and next-generation security cameras with PTZ functionality. Belden has also added direct-connect installations to our approved warranty list, meaning that REVConnect installers can terminate the 10GX Field-Mountable Plugs directly onto horizontal cable and receive a 25-year warranty to support their system.”
Selecting appropriate cabling to support power and data delivery is a many-faceted assignment. While the performance properties of twisted-pair cables are currently being examined closely by creators of standards, codes, and specifications, the performance of connecting hardware also plays an important role. As the examples in this article indicate, manufacturers continue to develop and refine connecting hardware to ensure it successfully supports data and power transmission.
Patrick McLaughlin is our chief editor.