IEC PAS 61156-1-4:2010

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

IEC/PAS 61156-1-4:2010(E) is covering exclusively four-pair data grade cables and 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.

General Information

• Status: Replaced
• Publication Date: 27-Jun-2010
• ICS: 33.120.20 - Wires and symmetrical cables
• Technical Committee: SC 46C - Wires and symmetric cables
• Drafting Committee: WG 7 - TC 46/SC 46C/WG 7
• Current Stage: DELPUB - Deleted Publication
• Completion Date: 11-Oct-2018

Relations

• Revised: IEC 61156-1-4:2018 - Multicore and symmetrical pair/quad cables for digital communications - Part 1-4: Assessment of conductor heating in bundled cables due to the deployment of remote powering
• Effective Date: 05-Sep-2023

Standards Content (Sample)

IEC/PAS 61156-1-4


®

Edition 1.0 2010-06



PUBLICLY AVAILABLE



SPECIFICATION



PRE-STANDARD
colour
inside

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




IEC/PAS 61156-1-4:2010(E)

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IEC/PAS 61156-1-4


®

Edition 1.0 2010-06



PUBLICLY AVAILABLE



SPECIFICATION



PRE-STANDARD
colour
inside

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



INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
X
ICS 33.120.20 ISBN 978-2-88912-032-1
® Registered trademark of the International Electrotechnical Commission

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– 2 – PAS 61156-1-4 © IEC:2010(E)



CONTENTS




FOREWORD.4



1 Scope.6


2 Normative references.8

3 Terms, definitions, symbols, units and abbreviated terms .8

3.1 Terms and definitions .8
3.2 Symbols, units and abbreviated terms.9
4 The testing of bundled cables .11
4.1 General comments .11
4.2 The bundling of cables.11
4.3 The suspension of the cable bundle .14
4.4 Assessment of the concatenated loop resistance of all pairs .16
5 The temperature as a function of the current load in conductors of bundled
cables in hexagonal densest packing structure.17
5.1 The test description .17
5.2 The temperature measurement .18
5.3 The heat generation and the resulting increase of the resistance.20
5.4 The specific resistivity referencing the IACS.24
6 Assessing already deployed cable systems .26
6.1 Background .26
6.2 The installed base .26
6.3 A simplified assessment of the installed base.27
7 The higher performing data grade cables .27
7.1 Conductor and cable diameters.27
8 The heat dissipation on heated and bundled cables.28
8.1 Radiation.28
8.2 Conduction .28
8.3 Convection .28
9 The heat dissipation in a heated conductor, pair or cable which has to be taken
into account.29

9.1 The heat dissipation of individual components.29
9.2 The heat dissipation of real cables.35
10 Thermodynamic considerations for a combined experimental and mathematical
solution of the heating problem .37
10.1 Objective .37
10.2 The cable bundle considered as a layered structure .37
10.3 The heat transfer through the layered structure .39
10.4 The heat transfer through the bundle in layered structure with internal heat
generation .40

Figure 1 – Lay-plate arrangement for stringing up and fixing the cables to maintain
the densest hexagonal packing structure, here shown for a 61-cable bundle .13
Figure 2 – Arrangement of cardboard–mask–plates over the ends of the cable
13
bundle to apply the insulating foam over the ends of the bundle.
Figure 3 – Schematic of the suspension of the cable bundle .15

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PAS 61156-1-4 © IEC:2010(E) – 3 –


Figure 4 – Cross-section of a cable bundle used for the test, here a bundle of 61

cables.17

Figure 5 – Connections on both ends of the center cable to obtain two nearly

identical “pair” resistances, which can then be measured using the voltage across

these pairs .19

Figure 6 – View of part of the cable bundle around the measurement cables

indicating the “temperature” measurement leads and those for the concatenation

between the cable layers in the bundle (here for n = 0 … 4) .19

Figure 7 – Schematic for connecting the cables in the different layers for
alternatively 2- and 4-pair heating.22

Figure 8 – Heat dissipation of a freely suspended conductor.29
Figure 9 – Heat dissipation of a single insulated conductor .30
Figure 10 – Dissipation of an unscreened twisted pair exposed to current heating.31
Figure 11 – Dissipation of a screened twisted pair exposed to current heating .32
Figure 12 – Heat dissipation in an unscreened cable .33
Figure 13 – Heat dissipation of an overall screened cable.34
Figure 14 – Heat dissipation in an individually screened pair cable with overall braid
or drain-wire with an overall metal / polymeric composite tape .34
Figure 15 – A data grade cable of arbitrary design .36
Figure 16 – Bundled cables indicating the air spaces between the cables .38
Figure 17 – The thermodynamic equivalent layered structure of the cables and air
gaps .38

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– 4 – PAS 61156-1-4 © IEC:2010(E)



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



FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote international
co-operation on all questions concerning standardization in the electrical and electronic fields. To this end and in
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preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with
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6) All users should ensure that they have the latest edition of this publication.
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent

rights. IEC shall not be held responsible for identifying any or all such patent rights.
A PAS is a technical specification not fulfilling the requirements for a standard, but made
available to the public.
IEC-PAS 61156-1-4 has been processed by subcommittee 46C: Wires and symmetric cables,
of IEC technical committee 46: Cables, wires, waveguides, R.F. connectors, R.F. and
microwave passive components and accessories.

The text of this PAS is based on the This PAS was approved for
following document: publication by the P-members of the
committee concerned as indicated in
the following document
Draft PAS Report on voting
46C/912/PAS 46C/918/RVD

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PAS 61156-1-4 © IEC:2010(E) – 5 –




Following publication of this PAS, which is a pre-standard publication, the technical committee

or subcommittee concerned may transform it into an International Standard.


This PAS shall remain valid for an initial maximum period of 3 years starting from the

publication date. The validity may be extended for a single period up to a maximum of 3 years,

at the end of which it shall be published as another type of normative document, or shall be

withdrawn.


A list of all parts of the IEC 61156 series, under the general title: Multicore and symmetrical

pair/quad cables for digital communications, can be found on the IEC website.


The 'colour inside' logo on the cover page of this publication indicates that it contains colours
which are considered to be useful for the correct understanding of its contents. Users should
therefore print this document using a colour printer.

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– 6 – PAS 61156-1-4 © IEC:2010(E)


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






1 Scope

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.

Hence, the main objective is
a) the indication of a suitable measuring method to assess the heating gradient across
bundled data grade cables subject to d.c. power transmission, using for the incident and
return conductors the common mode circuits of either two or four pairs;
b) to provide, toward this end, the worst case assessment of the conductor and cable heating
in bundled cable configurations, where the densest hexagonal packing configuration is
required. This assessment of the heating is anticipated to be carried out under the
extremely lenient condition of freely suspended cable bundles in an air-conditioned
environment free of any air draft, the heat dissipation thus being achieved by undisturbed

convection into the surrounding environment;
c) to provide some explanatory background information on the heat dissipation of heated
conductors, insulated conductors, pair and cables, both screened or unscreened;
d) to provide means to assess the installed base of data grade cables with a view to their
compliance with the requirements of either PoE or PoEP, if required in a comparative way,
but based on the resistance assessment of at least one short cable length withdrawn from
the installed base by replacement;
e) to indicate the basic physical assessment proceedure, based upon the testing of a cable
bundle according to item b). A comparable heating trial on the same cable bundle, but
under restricted heat dissipation conditions, yields then some indication of how to assess
the maximum occurring temperatures under these conditions;
f) towards this end, the densest hexagonal packing configuration has to be simplified, using
an equivalence in order to allow a consecutive evaluation of the heating under any heat
dissipation restriction using a layered structure of the cables and the interstitial air spaces
within the bundled structure.

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PAS 61156-1-4 © IEC:2010(E) – 7 –


For this purpose a test method is provided:


– to allow the evaluation of the heating of the conductors of cable bundles where all (or a

certain percentage of the cables) are exposed to powering. Additionally is considered

the case that either two of four pairs in a cable are used for d.c. power transmission;

N
⎛ ⎞

⎜ ⎟
– to measure the temperature of 1+ 6 ⋅ n cables in hexagonal densest packing
∑
⎜ ⎟

⎝ n=1 ⎠

structure, in order to allow the assessment of the temperature gradient and the heat

insulating properties of the cables. The densest packing of cables represents the worst
1

case situation ;

– to provide a means to assess the performance potential of an installed base of data
grade cables for power transmission. Evidently such a process has to take into account
the specified d.c. resistance for categorized cables. If an experimental assessment of
the installed cables is not feasible, then a normalizing procedure to IACS could be
envisioned, though the specified cable d.c. resistances are substantially below 100 %
IACS;
– to allow the assessment of the d.c. current transmission performance potential of the
newly developed cables (these cables may be made based on the most recent design
principles);
– to indicate a comparative test for a cable under 2- or 4-pair heating conditions and
under free and restricted heat dissipation conditions, as encountered for instance with
frame-wall, insulating material ducts etc.;
– to give the mathematical approach for this procedure;
– to allow also the extension of the results of two heating trials to any cable bundle size, i.e. also
to higher bundle sizes, provided the heat insulation conditions to which the cable
bundle is exposed to are known.
NOTE 2 The scope of this PAS exclusively covers the cable performances. The variable heat insulating properties
of the cables resulting out of the installation practices for channels (for instance feeding bundled cables through
insulating materials) is outside the scope of this PAS. This has to be initiated and be taken care of in ISO/IEC
JTC1/SC25 WG3 in a suitable technical report or installation guide. This is the reason that here only general
guidelines are given.
The test method described lends itself also to cable testing if higher currents than those resulting out of the basic
specified d.c. resistances and the specified currents for the IEEE 802.3 PoE / PoEP protocol are required. This
would eventually allow the transmission of higher powers at the same maximum ambient temperature of 60 ºC,
without exceeding the maximum permissible conductor temperatures in the cable. This may be applicable to higher
performing cable categories in cases where the user really needs the transmission of higher power levels than
anticipated in the IEEE 802.3 PoE / PoEP protocol.
In these cases, a verification of their conductor heating properties has to be assessed, and the cable performance
has to be guaranteed by the manufacturer.
The PAS is written in a general way, thus covering not only horizontal cables. Stranded cord cables will have to be

evaluated as well, and this very carefully, as they are so far installed in the equipment rooms in higher cable count
bundles as well. This PAS establishes some basic guidelines to deal with these problems.
The heating in this PAS is the result of the resistance which is specified in IEC 61156-5 and
IEC 61156-6 as 19 [ohm / 100 m] and 29 [ohm / 100 m].

1
Later in this document, a method is given to determine the equivalent diameters for bundles of densest packing,
having approximately the same dissipation properties with respect to convection and radiation. This may be
interesting for modelling purposes, in case a statistical current loading situation may have to be evaluated,
especially in cases where the convection is severely restrained due to surrounding insulation material or any
other means to prevent the targeted heat dissipation by radiation and convection.

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– 8 – PAS 61156-1-4 © IEC:2010(E)


2 Normative references


The following referenced documents are indispensable for the application of this document. For

dated references, only the edition cited applies. For undated references, the latest edition of

the referenced document (including any amendments) applies.


IEC 61156-1:2007, Multicore and symmetrical pair/quad cables for digital communications –

Part 1: Generic specification


IEC 61156-5:2009, Multicore and symmetrical pair/quad cables for digital communications –

Part 5: Symmetrical pair/quad cables with transmission characteristics up to 1 000 MHz –

Horizontal floor wiring – Sectional specification
IEC 61156-6:2010, Multicore and symmetrical pair/quad cables for digital communications –
Part 6: Symmetrical pair/quad cables with transmission characteristics up to 1 000 MHz – Work
area wiring – Sectional specification
IEEE 802.3af-2003, IEEE Standard for Information technology – Telecommunications and
information exchange between systems – Local and metropolitan area networks – Specific
requirements – Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
Access Method and Physical Layer Specifications – Amendment: Data Terminal Equipment
(DTE) Power via Media Dependent Interface (MDI)
IEEE 802.3at-2009 Part 3: Carrier Sense Multiple Access with Collision Detection (CSMA/CD)
Access Method and Physical Layer Specifications – Amendment 3: Data Terminal Equipment
(DTE) Power via the Media Dependent Interface (MDI) Enhancements
3 Terms, definitions, symbols, units and abbreviated terms
3.1 Terms and definitions
Open thermodynamic systems  - In this PAS, thermodynamic open systems are considered.
 Such systems differ from the usually considered
systems in the classic thermodynamics, which have
generally a constant mass flow going in and out over
the system borders. In the present case, the systems
have a constant mass flow equal to zero and an energy
transfer over the system borders, i.e. an energy influx
and/or outflux. This energy influx/outflux may be based
on electrical energy going into the system and being
transformed therein into heat or on any other kind of

heat transfer, be it by radiation, conduction or
convection, or any combination thereof.
Two-dimensional systems - In this PAS, a two-dimensional thermodynamic system
is understood as a cable or cable bundle which is
homogeneous in longitudinal direction, heated by an
electric energy influx, dissipating and/or absorbing
energy over the system borders in radial direction. The
dissipated and/or absorbed energy may be transferred
by radiation, conduction and convection or any
combination of the latter.

   Hence the cross-sectional system borders of a two-
dimensional system are subject to a radial energy flow,
which is only in case of a thermal equilibrium constant
and equal to the sum of the internally produced heat
and energy influx minus the energy outflux by
radiation, conduction and convection.

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PAS 61156-1-4 © IEC:2010(E) – 9 –


Excess energy - is the sum of the internally produced heat and energy

influx minus the energy outflux under thermal

equilibrium conditions. It is this excess heat which is

the culprit for the heat increase of the conductors.

Concatenation of systems - concatenations of thermodynamic systems are only

understood in this PAS as concatenations in any of the
radial directions, while all the concatenated systems have
the same longitudinal dimension.

Longitudinal open systems - such systems are understood here as systems which

in the main dimension – here the cable length – are

homogeneous with respect to the electrical energy

conversion into heat within the systems.

Electrical energy influx - is the electrical energy influx over the open thermodynamic
system borders at one or both ends of their
longitudinal extensions (this allows the very unlikely
testing under a powering of the pairs from either one
or both sides open)
Internally generated heat - is the internally generated heat by the electric influx
2
corresponding to I ·R·t [Watt·sec/ length] and is length
homogeneous, i.e. constant over the length.
Radial energy in – or outflux - is the energy either picked up over the radial borders
of the system or increments thereof or the radial
outflux of energy out of the system or increments
thereof. Both the influx and the outflux can occur for
bundled cables by radiation, conduction and
convection or any combination thereof.

NOTE As a result of the above definitions, any cable is considered to heat up homogeneously over its length in the
described bundled systems, and this independently of reaching the thermal equilibrium. If the above-system
definitions are not met, then the cable heats up inhomogeneously over its length – dependent upon the locally
varying dissipation conditions length –resulting in a length distributed resistance increase. This may happen under
installation conditions, when the heat dissipation is restricted locally over the length of the cable bundles. This may
easily yield local conductor temperatures which substantially exceed the maximum specified temperature of 60 ºC.
As this aspect has to be considered more in detail in the appropriate installation guidelines, it is outside the scope of
this report.
This report will however adress the subject of restricted heat dissipation as a guide to developing the appropriate
installation guidelines.
3.2 Symbols, units and abbreviated terms

N number of cables in the bundle [ - ]
n number of cable layers around the centre conductor [ - ]
R round trip loss of a pair in the cable [Ω/100 m]
Ri

R resistance of the concatenated quad conductors of a cable for one- or two-pair
B
heating at 20 °C [Ω/l ] or
...