ISO/IEC TS 29125:2017 pdf download – Information technology – Telecommunications cabling requirements for remote powering of terminal equipment.
3.1 .1 power source equipment equipment that provides power 3.1 .2 cable bundle several cables tied together or in contact with one another in a parallel configuration for at least 1 m, with the cross-section profile of the arrangement basically circular 3.1 .3 conductor element intended to carry electric current [SOURCE IEC 60050-1 51 :2001 , 1 51 -1 2-05, modified – The 3 Notes have been deleted.] 3.1 .4 current carrying capacity maximum current a cable circuit (one or several conductors) can support resulting in a specified increase of temperature of the conductor beyond the ambient temperature, not exceeding the maximum allowed operating temperature of the cable [SOURCE: IEC 61 1 56-1 :2007/AMD1 :2009, 3.24, modified – “increase of temperature” has replaced “increase of the surface temperature”.] 3.1 .5 remote powering supply of power to application specific equipment via balanced cabling 3.1 .6 temperature rise difference in temperature between the initial temperature of the conductor without power and the final temperature of the powered conductor at steady state
5 Cabling selection and performance Cabling for remote powering should be implemented using 4-pair balanced cabling. This cabling will be used simultaneously to support signal transmission and remote power feeding for the terminal equipment. This document assumes the use of balanced cabling components specified in the reference implementation clause of the relevant design standards of the ISO/IEC 1 1 801 series. The transmission parameters of balanced cables related to remote powering can be found in Annex C. 6 Installation conditions 6.1 General Cabling may be installed in different types of continuous and non-continuous pathway systems as described in ISO/IEC 1 4763-2. The installation of a cable within the pathway systems should take into account the specified operating temperature of the cable. Due to the Joule effect, each energized conductor has a temperature rise. Larger cable bundles have more heat generation and therefore the temperature rise is worse than smaller cable bundles. The cable bundle size is limited by the current capacity in 6.3 and the induced temperature rise that results in an operating temperature of the cable, not to exceed its temperature rating. The following guidelines for pathway selection and installation should be considered: a) installation design including the type of pathways selected, the pathway fill factor, whether the pathway is sealed at both ends, b) the pathway environment and whether the pathway goes through thermally insulated areas, in which case the type of insulation will be a significant factor. For optimal thermal performance, pathway design should avoid any insulated areas, c) thermal aspects of the entire pathway (e.g. open tray, closed tray, ventilated, non- ventilated, plastic conduit, metal conduit, fire barriers) should be taken into account.
6.2 Ambient temperature Different segments of a link can have different ambient temperatures, which can influence the amount of remote power that can be delivered. Therefore the ambient temperature in different length segments of a link or channel has a direct impact on the operating temperature of the cable used for the link or channel and can limit the capability of the cable for remote power delivery to powered terminal equipment. The worst case installed cabling condition with respect to the maximum ambient temperature shall be used to determine the maximum operating temperature for a link or channel when subject to remote powering. 6.3 Temperature rise and current capacity When remote power is applied to balanced cabling, the temperature of the cabling will rise due to resistive heat generation (Joule effect) in the conductors. Depending on cable construction and installed cabling conditions, the heat generated will be dissipated into the surrounding environment until a steady state is reached with the temperature of the cable bundle (operating temperature) higher than the ambient temperature of the surrounding environment. The maximum temperature of any cable shall not exceed the temperature rating of the cable. The standards in the ISO/IEC 1 1 801 series require this temperature to be 60 °C (minimum).