Investigations of the thermal impact of remote powering over generic cabling

Transcription

1 Investigations of the thermal impact of remote powering over generic cabling Presented by Alan Flatman, LAN Technologies Prepared by Mike Gilmore, e-ready Building Limited, UK Arne Keller, Commscope, Sweden

2 ISO/IEC TR ANSI/TIA-TSB-184 ISO/IEC TR Guidelines for Supporting Power Delivery Over Balanced Twisted-Pair Cabling Information technology - Telecommunications cabling guidelines for remote powering of terminal equipment Based on information from TIA (TIA-TSB-184) and ISO/IEC (TR 29125) Category 5/5e cables in a bundle Open air ventilation All pairs powered Current per pair Temperature rise (deg C) IEEE 802.3at Type 2: 300 ma per conductor/600 ma per pair

3 Further Investigation ISO/IEC TR ANSI/TIA-TSB-184 Thermal assessment based on bundles on cables in ventilated conditiions EN :2011 ISO/IEC ANSI/TIA-568-C.2 specify channel and permanent link (link segment performance) requirements for dc loop resistance ensuring enough power reaches the PD IDENTIFIED AND UNADDRESSED PROBLEM AREAS Remote powering at levels in excess of IEEE 802.3at Type 2 Design, planning and installation issues for widespread implementation of remote powering Loophole conformance to ISO/IEC 11801/EN x Real installation conditions High resistance cables Excess thermal impact Link length reductions De-mating points copper coated elements 24 AWG conductors

4 Increasing Power/Current Example Example

5 Installation Conditions Typical bundle size is 24 cables but installation conditions will affect thermal impact Fully ventilated Partially ventilated Unventilated Insulated

6 Channel Specification EN :2011 ISO/IEC Information technology - Generic cabling systems: General requirements Information technology - Generic cabling systems: General requirements EQP Channel TE DC loop resistance (maximum) Class C Classes D 40 Ω 25 Ω No length dependence UNINTENDED CONSEQUENCES The use of smaller copper conductors (higher Ω/m) on shorter channels The use of non-copper conductors (higher Ω/m) on shorter channels

7 CLC TR CLC TR Information technology - Cabling installation: Remote powering Work began: 2012 Publication: 2015 probable OBJECTIVES 1 Definition of a test configuration to assess thermal impact of remote powering 2 Testing of different installation conditions and currents 3 4 Development of a modelling tool to enable predictions of thermal impact The production of requirements/recommendations for cabling installation, planning and operation OPENING POSITION None of the CENELEC experts were aware of any problem caused by cable heating where current levels are in accordance with IEEE 802.3at and therefore did not anticipate any need for additional installation or operational instructions for cabling in support of IEEE 802.3at.

8 Objective 1 - Test Configuration CURRENT FEED USING 37 CABLE BUNDLE i c... i c Cable 1 Cable 2 Cable 37 T 2c T 2d T 2b T 1, T 2a and T 3 Thermocouples T 1 0,6 ± 0,05 m T 2x 0,6 ± 0,05 m T 3 T a Ambient 1,2 m 1,2 m perfect bundle

9 Objective 2 - Initial Results INITIAL RESULTS USING CENELEC TEST CONFIGURATION and CATEGORY 6 U/UTP CABLES T 2a - T ambient 37 cables Fully ventilated Steady state 300 ma per conductor: all pairs powered 1.2 o C 450 ma per conductor: all pairs powered 4.3 o C 900 ma per conductor: all pairs powered 20 o C 300 ma per conductor: all pairs powered 5 o C 7 o C 37 cables Fully insulated 450 ma per conductor: all pairs powered 11 o C 17 o C 900 ma per conductor: all pairs powered 49 o C 75 o C After 120 minutes After 425 minutes Steady state

10 Initial Conclusions Early work, using a standardized test configuration, has looked at bundles of 37 cables in both fully ventilated and heavily insulated conditions which are considered to reflect best and worst case thermal scenarios. This work indicates that for a 4-pair current of 300 ma per conductor (600 ma per pair), the temperature increase seen at the centre of a heavily insulated cable bundle does not exceed the 10 o C previously considered by IEEE. The above statement assumes the use of cabling channels in accordance with Class D (or above) as referenced by IEEE 802.3at. However, it is also critical to ensure that the relevant parts of the link segment (IEEE) and channel (ISO/IEC and CLC) are specified with a dc loop resistance per unit length requirement.