International Electrotechnical Commission

Multicore and symmetrical pair/quad cables for digital communications – Part 1-4: Symmetrical pair/quad cables with transmission characteristics up to 1 000 MHz – Conductor heating of bundled data grade cables for limited power transmission based on IEEE 802.3 - Edition 1.0
 N PAS 61156-1-4

Annotation

This PAS is a technical supplement to IEC 61156-1, edition 3 (2007): Multicore and symmetrical pair/quad cables for digital communications – Part 1: Generic specification.

This PAS, covering exclusively four-pair data grade cables, is intended to provide a test method for the determination of the maximum attained conductor temperatures which occur due to the deployment of the IEEE protocol for PoE /PoEP.

It gives as well the required background information about the thermodynamic behaviour of such bundled cables, if they are located in areas with restricted heat dissipation, a reality which occurs in every installation situation. However, only the basic principles are given, as the rigorous application and solution of these problems fall into the relevant cabling standards.

NOTE 1 The restriction to four-pair data grade cables is very important, as the heating of a multiple pair cable, especially if it has a protective screen, is much worse, since the ratio of the heat generation within the cross-section versus the overall circumferential surface to dissipate the heat is dramatically decreased, thus yielding substantially higher conductor temperatures. Additionally, the screen acts as a near perfect IR–reflector, thus increasing additionally only the excess heat within the cable.

This restriction is of importance considering the installed base, where individual four-pair cables in a loose bundle arrangement may need to replace multiple pair cables.