ISO/IEC TS 29125:2017

ISO/IEC TS 29125
Edition 2.0 2017-04
TECHNICAL
SPECIFICATION
colour
inside
Information technology – Telecommunications cabling requirements for remote
powering of terminal equipment

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ISO/IEC TS 29125
Edition 2.0 2017-04
TECHNICAL
SPECIFICATION
colour
inside
Information technology – Telecommunications cabling requirements for remote

powering of terminal equipment

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 35.200 ISBN 978-2-8322-4223-0

– 2 –  ISO/IEC TS 29125:2017 © ISO/IEC 2017
CONTENTS
FOREWORD . 4
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms, definitions and abbreviated terms . 7
3.1 Terms and definitions . 7
3.2 Abbreviated terms . 8
4 Conformance . 8
5 Cabling selection and performance . 9
6 Installation conditions . 9
6.1 General . 9
6.2 Ambient temperature. 9
6.3 Temperature rise and current capacity . 9
6.4 Factors affecting temperature increase . 11
6.4.1 General . 11
6.4.2 Installation near equipment . 11
6.4.3 Cable count within a bundle . 11
6.4.4 Reducing temperature increase . 12
6.4.5 Cable bundle suspended in air . 13
6.4.6 Administration. 14
7 Remote power delivery over balanced cabling . 14
8 Connecting hardware . 15
Annex A (informative) Mitigation considerations for installed cabling . 17
A.1 General . 17
A.2 Minimum cabling class . 17
A.3 Bundle size and location . 17
A.4 Mitigation options . 17
Annex B (informative) Modelling temperature rise for cable types, bundle sizes and
installation conditions . 18
B.1 Model basics . 18
B.2 Power dissipated (P) . 18
B.3 Temperature difference from ambient temperature to bundle surface (∆T ) . 19
u
B.3.1 Model equations . 19
B.3.2 Typical values for constant ρ . 19
u
B.4 Temperature difference from bundle surface to bundle centre (∆T ) . 19
th
B.4.1 Model equations . 19
B.4.2 Typical values for constant ρ . 19
th
B.5 Temperature variation within the bundle (∆T(x)) . 20
B.6 Alternative presentation of the model . 20
B.7 Adaptation model used to derive temperature rise vs. cables in a bundle . 20
B.8 Calculations . 21
B.9 Example. 21
B.10 Coefficients for air and conduit. 22
Annex C (informative) Transmission parameters related to remote powering. 23
C.1 DC loop resistance. 23

C.2 DC resistance unbalance (within pair) . 23
C.3 DC resistance unbalance (pair to pair) . 24
Annex D (informative) Illustrations of heating of various bundle sizes and
configurations . 26
D.1 Limiting cable bundle size . 26
D.2 Separating into smaller bundles . 27
Annex E (informative) Test protocol . 28
E.1 Background. 28
E.2 Test set-up . 28
Annex F (informative) Detailed test procedure . 30
F.1 General . 30
F.2 Test set-up . 30
F.2.1 Thermocouple placement . 30
F.2.2 Measurement of cable bundle in air . 31
F.2.3 Measurement of cable bundle in conduit . 32
Bibliography . 34

Figure 1 – Examples of end point powering systems using signal pairs (top) and spare
pairs (bottom) . 14
Figure 2 – Examples of mid-span powering systems . 15
Figure B.1 – Temperature rise profile . 18
Figure D.1 – 91-cable bundle . 26
Figure D.2 – Three bundles of 37 cables . 26
Figure D.3 – Three bundles of 37 cables with separation . 27
Figure E.1 – 37-cable bundle and temperature location. 28
Figure E.2 – "Perfect bundle" and thermocouple configuration . 29
Figure E.3 – Conductor configuration . 29
Figure F.1 – Placement of thermocouple . 30
Figure F.2 – Securing of the thermocouple. 31
Figure F.3 – Test set-up for cable bundles in air . 32
Figure F.4 – Test set-up for cable bundles in conduit . 33

Table 1 – Maximum current per conductor versus temperature rise in a 37-cable
bundle in air and conduit (all 4 pairs energized) . 10
Table 2 – Calculated worst case current per conductor versus temperature rise in a
bundle of 37 4-pair cables (all pairs energized) . 11
Table 3 – Temperature rise versus cable bundle size (500 mA per conductor) . 12
Table 4 – Temperature rise for a type of cable versus the number of energized pairs in
a 37-cable bundle (500 mA per conductor) . 13
Table B.1 – Bundling coefficients for different types of cables and cords (all 4 pairs
energized) . 22
Table C.1 – Maximum DC loop resistance of channels . 23
Table C.2 – DC resistance unbalance of cables, connecting hardware and channels . 24
Table C.3 – DC resistance unbalance (pair to pair) . 25

– 4 –  ISO/IEC TS 29125:2017 © ISO/IEC 2017
INFORMATION TECHNOLOGY –
TELECOMMUNICATIONS CABLING REQUIREMENTS
FOR REMOTE POWERING OF TERMINAL EQUIPMENT

FOREWORD
1) ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees established
by the respective organization to deal with particular fields of technical activity. ISO and IEC technical
committees collaborate in fields of mutual interest. Other international organizations, governmental and non-
governmental, in liaison with ISO and IEC, also take part in the work. In the field of information technology,
ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
2) The formal decisions or agr
...