EuroWire May 2015

Technical article

The increasing demand for more power supplied from the Power PSE to the PD is obvious, with powering over all four pairs expected to be IEEE standardised [11] and a variety of non-standard products currently available on the market which provide power levels in excess of those stated in IEEE 802.3at. Higher power levels will increase perfor- mance risk, but will also allow PoE to be used for a wider range of applications. Conclusions A two-dimensional model was set up using COMSOL Multiphysics software in order to replicate measured results. A test method proposed by IEC subcommittee 46C to assess cables for Power over Ethernet was followed, which outlined the measurement for heating data cables by DC current. Excellent correlation between simulated and measured results for a single cable has been demonstrated. This correlation encourages use of the software for the thermal prediction of cables in densely populated networks. It is also expected to provide a strong indication of the temperature rise for varying bundle sizes, ambient temperatures, and containment systems, etc. The thermal performance of a CCA cable subjected to DC powering has also been proven to radiate more heat than cables which use solid copper conductors using equal DC current values. Installations using PoE technology differ greatly in terms of their configuration and environment. With an increasing demand for more power, which is likely to require powering over all four pairs, further work is required to investigate cable and component performance in areas such as bundled cables, thermal behaviour in different ambient temperature environments, cable reach under PoE, and connector demating under load. n

[6] National Instruments LabVIEW: www.ni.com/ labview [7] Minitab: www.minitab.com [8] J Wilson and C Hernández-Hall, Physics Laboratory Experiments, Brooks/Cole, p 361 (2009) [9] F S Akinnuoye, H Sasse, V Kang, A Duffy, ‘Heating Effects on channel performance for Power over Ethernet (PoE) applications,’ Proceedings of the International Wire & Cable Symposium (IWCS), November, 2013 [10] H Congdon, B Davis, ‘Mythbusting takes on shielded cabling,’Bicsi Presentation, 2009 [11] Four-pair PoE study group: www.ieee802. org/3/4PPOE Paper courtesy of the 63 rd IWCS Technical Symposium, Providence, Rhode Island, USA, November 2014.

References

Brand-Rex Ltd Glenrothes Fife United Kingdom Tel : +44 1592 778459

IEEE Standard 802.3at, 2009

[1]

[2] M Gilmore, ‘The impact of copper clad aluminium (and steel) conductors within balanced pair cables (intended for use within implementations of generic cabling),’FIA-IAN-002, 2011 [3] IEC Subcommittee 46C, ’Proposal for measuring of heating of data cables by current,’ 46C/906/NP, 2009 [4] COMSOL Multiphysics: www.comsol.com [5] G J Anders, Rating of Electric Power Cables in Unfavorable Thermal Environment, Wiley- Blackwell, pp 2-4 (2004)

Email : ssimms@brand-rex.com Website : www.brand-rex.com

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May 2015