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802.3 PoE | Datcom

Emerging high powered PoE & Connecting Hardware for IEEE 802.3bt and Beyond

Proliferation of Power over Ethernet (PoE) enabled devices and systems continues to drive the need for higher levels of DC power over structured cabling systems. This is being driven by a rapid increase in the total number of PoE devices deployed with each device requiring more power. Through the iterations of IEEE 802.3af, IEEE 802.3at and now IEEE 802.3bt, the maximum current drawn across the cabling infrastructure has been continuously escalating. Although most PoE systems do not utilize the maximum allowable currents on all four pairs, the proposed application standard (IEEE 802.3bt) specifies that up to 1A per pair can be supplied to the device over the structured wiring system.
Concurrently, the TIA is developing TSB-184-A which describes the steps recommended to support these increasing power requirements. Maximum current levels for a structured cabling system are set based on; copper cross sectional area, de-rating necessary for bundling, maximum cable capacity, the maximum environmental temperature, and the maximum allowable temperature rise in the cable. It has been assumed that connectors do not represent the limiting factor in the system. Table 1 provides a listing of requirements across a number of established standards for supporting power delivery over balanced twisted-pair cabling. This assumption is generally correct. 

However, improperly designed connectivity may not support the required current without detrimental effects. In addition to normal UL and NEC safety standards, the next level of verification assures that the connectors can continuously conduct required current levels without overheating. Excessive heating can reduce electrical performance characteristics of connectors. Plus, heat can increase the likelihood of failure in the form of trace severing or de-lamination of the printed circuit board FR4 substrate. New standards allow for power insertion on all four pair combinations. As a result, the maximum expected current through a connector is 1A on each of the four pairs.

Learn more about how Hubbell Connectivity is fully capable of handling current levels that exceeds the proposed PoE specifications withouy, any substantial increas in temperature or failure.