ETSI EN 300 253 V2.2.1 (2015-06)

ETSI EN 300 253 V2.2.1 (2015-06)






EUROPEAN STANDARD
Environmental Engineering (EE);
Earthing and bonding of ICT equipment powered by -48 VDC in
telecom and data centres

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2 ETSI EN 300 253 V2.2.1 (2015-06)



Reference
REN/EE-0250
Keywords
bonding, earthing, equipment practice
ETSI
650 Route des Lucioles
F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: +33 4 92 94 42 00  Fax: +33 4 93 65 47 16

Siret N° 348 623 562 00017 - NAF 742 C
Association à but non lucratif enregistrée à la
Sous-Préfecture de Grasse (06) N° 7803/88

Important notice
The present document can be downloaded from:
http://www.etsi.org/standards-search
The present document may be made available in electronic versions and/or in print. The content of any electronic and/or
print versions of the present document shall not be modified without the prior written authorization of ETSI. In case of any
existing or perceived difference in contents between such versions and/or in print, the only prevailing document is the
print of the Portable Document Format (PDF) version kept on a specific network drive within ETSI Secretariat.
Users of the present document should be aware that the document may be subject to revision or change of status.
Information on the current status of this and other ETSI documents is available at
http://portal.etsi.org/tb/status/status.asp
If you find errors in the present document, please send your comment to one of the following services:
https://portal.etsi.org/People/CommiteeSupportStaff.aspx
Copyright Notification
No part may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying
and microfilm except as authorized by written permission of ETSI.
The content of the PDF version shall not be modified without the written authorization of ETSI.
The copyright and the foregoing restriction extend to reproduction in all media.

© European Telecommunications Standards Institute 2015.
All rights reserved.

TM TM TM
DECT , PLUGTESTS , UMTS and the ETSI logo are Trade Marks of ETSI registered for the benefit of its Members.
TM
3GPP and LTE™ are Trade Marks of ETSI registered for the benefit of its Members and
of the 3GPP Organizational Partners.
GSM® and the GSM logo are Trade Marks registered and owned by the GSM Association.
ETSI

---------------------- Page: 2 ----------------------
3 ETSI EN 300 253 V2.2.1 (2015-06)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 5
Introduction . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 6
3 Definitions and abbreviations . 7
3.1 Definitions . 7
3.1.1 IEC definitions (by IEC 60050 numbers) . 7
3.1.2 Telecommunication definitions . 8
3.2 Abbreviations . 9
4 General requirements . 9
4.1 Safety from electrical hazards . 9
4.2 Signal reference . 10
4.3 EMC performance . 10
5 Requirements on bonding networks . 10
5.1 Bonding configurations . 10
5.2 CBN within a telecommunication building or data centre . 10
5.3 BN within a telecommunication or ICT system . 10
5.4 Merging of CBN and MESH-BNs . 13
5.5 Cabling within and between BNs . 13
6 Requirements for power distribution . 13
6.1 DC power distribution of secondary supply . 13
6.2 DC power distribution of tertiary supplies . 13
6.3 AC mains distribution and bonding of the protective conductor . 14
6.4 AC power distribution from tertiary power supply . 14
Annex A (normative): Rationale about CBN co-ordination . 15
Annex B (informative): Rationale about the integration of the DC return conductor into the
merged CBN/MESH-BN . 16
Annex C (normative): AC mains distribution and bonding of the protective conductor . 18
Annex D (informative): Bibliography . 22
History . 23

ETSI

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4 ETSI EN 300 253 V2.2.1 (2015-06)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://ipr.etsi.org).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Environmental Engineering (EE).
The present document has been produced within the framework of the following considerations:
a) ICT equipment is generally installed in telecommunication or data centres and held in racks, cabinets or other
mechanical structures;
b) the existing Recommendation ITU-Ts and CENELEC standards in such matters do not ensure the required
standardization at the equipment level;
c) network operators and equipment providers agreed to standardize on a bonding configuration that facilitates:
- compliance with functional requirements including Electromagnetic Compatibility (EMC) aspects of
emission and immunity;
- compatible building and equipment provisions;
- installation of new telecommunication or data centres as well as expansion or replacement of
installations in existing telecommunication or data centres with equipment coming from different
suppliers;
- a structured installation practice;
- simple maintenance rules;
- contracting on a common basis;
- cost effectiveness in development, manufacturing, installation and operation.

National transposition dates
Date of adoption of this EN: 26 May 2015
Date of latest announcement of this EN (doa): 31 August 2015
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 29 February 2016
Date of withdrawal of any conflicting National Standard (dow): 29 February 2016

ETSI

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5 ETSI EN 300 253 V2.2.1 (2015-06)
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
The present document addresses earthing and bonding of ICT equipment in telecommunication or data centres in
relation to safety, functional performance and EMC.
Information regarding the general principles on earthing for telecommunication or data centres has been published by
the ITU-T in the handbook on "Earthing of telecommunication installations" [i.1]. Recommendation ITU-T K.27 [i.2]
deals with bonding configurations and earthing inside a telecommunication building or data centre. One bonding
configuration only is selected from Recommendation ITU-T K.27 [i.2] (CBN/MESH-BN) and tailored to the present
document.
The author thanks the International Electrotechnical Commission (IEC) for permission to reproduce Information from
its International Standard IEC 60364-1 (CENELEC HD 60364-1 [i.11]) ed. 5.0 (2005). All such extracts are copyright
of IEC, Geneva, Switzerland. All rights reserved. Further information on the IEC is available from www.iec.ch. IEC has
no responsibility for theplacement and context in which the extracts and contents are reproduced by the author, nor is
IEC in any wayresponsible for the other content or accuracy therein.
ETSI

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6 ETSI EN 300 253 V2.2.1 (2015-06)
1 Scope
The present document applies to earthing and bonding of ICT equipment operating with DC voltage defined in ETSI
EN 300 132-2 [i.9], in order to facilitate the installation, operation and maintenance of equipment.
It also co-ordinates with the pre-conditions of the installation to achieve the following targets:
- safety from electrical hazards;
- reliable signal reference;
- satisfactory Electromagnetic Compatibility (EMC) performance.
The specification of ICT equipment and of the pre-conditions of installation are subject to agreement of the parties (e.g.
the supplier and the purchaser) and the procedure to achieve agreement is covered by annex A of the present document.
The present document does not cover safety and EMC aspects of the equipment. Those aspects are covered by other
relevant standards.
The present document does not apply to the installation of ICT equipment in locations other than telecommunication
and data centres, e.g. ICT equipment within a customer's building, including subscriber line termination.
NOTE: Earthing and bonding of equipment installed in locations other than telecommunication and data centres
is covered by CENELEC EN 50310 [i.6].
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] CENELEC HD 60364-4-41: "Low-voltage electrical installations - Part 4-41: Protection for safety
- Protection against electric shock".
[2] CENELEC HD 60364-5-54: "Low-voltage electrical installations - Part 5-54: Selection and
erection of electrical equipment - Earthing arrangements, protective conductors and protective
bonding conductors".
[3] CENELEC EN 60950-1: "Information technology equipment - Safety - Part 1: General
requirements".
[4] CENELEC EN 41003: "Particular safety requirements for equipment to be connected to
telecommunication networks and/or a cable distribution system".
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
ETSI

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7 ETSI EN 300 253 V2.2.1 (2015-06)
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ITU-T handbook: "Earthing of telecommunication installations".
[i.2] Recommendation ITU-T K.27 (1991): "Bonding Configurations and Earthing inside a
Telecommunication Building".
[i.3] IEC 60050: "International Electrotechnical Vocabulary".
[i.4] IEC 60050-604: "International Electrotechnical Vocabulary. Chapter 604: Generation,
transmission and distribution of electricity - Operation".
[i.5] IEC 60050-826: "International Electrotechnical Vocabulary. Electrical installations of buildings".
[i.6] CENELEC EN 50310: "Application of equipotential bonding and earthing in buildings with
information technology equipment".
[i.7] CENELEC EN 62305 series: "Protection against lightning".
[i.8] IEC 60050-195: "International Electrotechnical Vocabulary. Electrical installations of buildings".
Earthing and protection against electric shock.
[i.9] ETSI EN 300 132-2: "Environmental Engineering (EE); Power supply interface at the input to
telecommunications and datacom (ICT) equipment; Part 2: Operated by -48 V direct current (dc)".
[i.10] CENELEC EN 50162: "Protection against corrosion by stray current from d.c. system".
[i.11] CENELEC HD 60364-1: "Electrical installation of buildings; Part 1: Scope, object and
definitions".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply.
The following definitions with respect to earthing and bonding are introduced by the IEC 60050 [i.3] and are used
within the present document to maintain conformity.
3.1.1 IEC definitions (by IEC 60050 numbers)
NOTE: IEC 60050 [i.3] references are given in parentheses (see IEC 60050-604 [i.4], IEC 60050-826 [i.5] and
IEC 60050-195 [i.8]).
earth (195-01-03): part of the Earth which is in electric contact with an earth electrode and the electric potential of
which is not necessarily equal to zero earthing arrangement
earthing conductor (195-02-03): conductor which provides a conductive path, or part of the conductive path, between
a given point in a system or in an installation or in equipment and an earth electrode
earth electrode (195-02-01): conductive part, which may be embedded in a specific conductive medium, e.g. concrete
or coke, in electric contact with the Earth
earthing network (604-04-07): part of an earthing installation that is restricted to the earth electrodes and their
interconnections
equipotential bonding (195-01-10): provision of electric connections between conductive parts, intended to achieve
equipotentiality
main earthing terminal (826-13-15): terminal or busbar which is part of the earthing arrangement of an installation
and enabling the electric connection of a number of conductors for earthing purposes
ETSI

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8 ETSI EN 300 253 V2.2.1 (2015-06)
Neutral conductor (N) (826-01-03): conductor connected to the neutral point of a system and capable of contributing
to the transmission of electrical energy
PEN conductor (826-13-25): conductor combining the functions of both a protective earthing conductor and a neutral
conductor
protective earthing conductor (PE) (826-13-23): protective conductor provided for protective earthing
IT, TN-C, TN-S, and TT systems (see HD 60 364-1: The codes used have the following meanings:
First letter – Relationship of the power system to earth:
T = direct connection of one point to earth;
I = all live parts isolated from earth, or one point connected to earth through a high impedance.
Second letter – Relationship of the exposed-conductive-parts of the installation to earth:
T = direct electrical connection of exposed-conductive-parts to earth, independently of the earthing of any point of the
power system;
N = direct electrical connection of the exposed-conductive-parts to the earthed point of the power system
Subsequent letter(s) (if any) – Arrangement of neutral and protective conductors:
S = protective function provided by a conductor separate from the neutral conductor or from the earthed line conductor.
C = neutral and protective functions combined in a single conductor (PEN conductor).
3.1.2 Telecommunication definitions
The following definitions, specific to telecommunication or data centre installations and not covered by the
IEC 60050 [i.3], are used within the present document. Correspondence to Recommendation ITU-T K.27 [i.2] is
indicated as appropriate.
bonding mat: essential means to provide a SRPP by a discernible, nearly regular mesh structure
NOTE: The bonding mat may be located either below or above a collection of equipment constituting a system
block.
Bonding Network (BN), (Recommendation ITU-T K.27 [i.2]): set of interconnected conductive structures that
provides an "electromagnetic shield" for electronic systems and personnel at frequencies from Direct Current (DC) to
low Radio Frequency (RF)
NOTE: The term "electromagnetic shield" denotes any structure used to divert, block or impede the passage of
electromagnetic energy. In general, a BN need not be connected to earth but all BNs considered in the
present document will have an earth connection.
Common Bonding Network (CBN), (Recommendation ITU-T K.27 [i.2]): principal means for effective bonding and
earthing inside a telecommunication building or data centre
NOTE: It is the set of metallic components that are intentionally or incidentally interconnected to form the
principal BN in a building. These components include: structural steel or reinforcing rods, metallic
plumbing, Alternating Current (AC) power conduit, PE conductors, cable racks and bonding conductors.
The CBN always has a mesh topology and is connected to the earthing network.
DC return conductor: (+) conductor of the -48 V or -60 V secondary DC supply
ICT equipment: equipment designed for Information and Communication Technologies
NOTE: It is similar to Information Technology (IT), but focuses primarily on communication technologies. This
includes the Internet, wireless networks, cell phones, and other communication mediums.
MESHed Bonding Network (MESH-BN), (Recommendation ITU-T K.27 [i.2]): bonding network in which all
associated equipment frames, racks and cabinets and usually the DC power return conductor, are bonded together as
well as at multiple points to the CBN
NOTE 1: Consequently, the MESH-BN augments the CBN.
NOTE 2: See figure 1 of the present document.
ETSI

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9 ETSI EN 300 253 V2.2.1 (2015-06)
MESHed Isolated Bonding Network (MESH-IBN), (Recommendation ITU-T K.27 [i.2]): type of IBN in which the
components of the IBN (e.g. equipment frames) are interconnected to form a mesh-like structure
NOTE: This may, for example, be achieved by multiple interconnections between cabinet rows, or by connecting
all equipment frames to a metallic grid (a "bonding mat") extending beneath the equipment. The bonding
mat is, of course, insulated from the adjacent CBN. If necessary the bonding mat could include vertical
extensions, resulting in an approximation to a Faraday cage. The spacing of the grid is chosen according
to the frequency range of the electromagnetic environment.
power supply:
- primary supply: public mains or, under emergency conditions, a locally generated AC supply
- secondary supply: supply to the ICT equipment, racks or system block, derived from the primary supply
- tertiary supplies: supplies to the ICT equipment, derived from the secondary supply
system: regularly interacting or interdependent group of items forming a unified whole
system block: functional group of equipment depending in its operation and performance on its connection to the same
system reference potential plane, inherent to a MESH-BN
System Reference Potential Plane (SRPP): conductive solid plane, as an ideal goal in potential equalizing, is
approached in practice by horizontal or vertical meshes
NOTE 1: The mesh width thereof is adapted to the frequency range to be considered. Horizontal and vertical
meshes may be interconnected to form a grid structure approximating to a Faraday cage.
NOTE 2: The SRPP facilitates signalling with reference to a common potential.
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Alternating Current
BN Bonding Network
CBN Common Bonding Network
DC Direct Current
EMC ElectroMagnetic Compatibility
LPS Lightning Protection System
MESH-BN MESHed Bonding Network
MESH-IBN MESHed Isolated Bonding Network
N Neutral conductor
PE Protective Earth conductor
PEN combined Protective Earth and Neutral conductor
RF Radio Frequency
SRPP System Reference Potential Plane
4 General requirements
4.1 Safety from electrical hazards
To achieve safety the standards EN 60950-1 [3], EN 41003 [4] and CENELEC HD 60364-4-41 [1] shall be applied in
the design of the equipment. The installation of PEs and equipotential bonding conductors shall be carried out in
accordance with CENELEC HD 60364-5-54 [2].
The conductors involved shall provide sufficiently high current conducting capability and low impedance according to
the relevant safety standards to avoid electric shock, risk of fire, or damage to the equipment under normal or faulty
operating conditions within an equipment or the distribution network, or due to the impact of induced voltage and
current, e.g. by lightning.
ETSI

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10 ETSI EN 300 253 V2.2.1 (2015-06)
4.2 Signal reference
Reliable signal reference shall be provided by a SRPP dedicated at least to a functional unit or a system block. To avoid
undue functional distortion or risk of component failure, the SRPP shall provide sufficiently low impedance up to the
highest frequency to be regarded by using a metal plane or a meshed configuration having adequate mesh dimensions,
e.g. a bonding mat. The frequency band to be covered shall include the spectral components of transients caused by
switching, short circuits and atmospheric discharges.
NOTE: Signal reference to the SRPP does not always imply signal return via the SRPP.
4.3 EMC performance
Measures to gain a satisfactory EMC performance shall be assisted by a SRPP. The SRPP shall provide sufficiently low
impedance for efficient connection of filters, cabinets and cable shields. The requirement to avoid undue emission of, or
susceptibility to electromagnetic energy under normal operating conditions may govern the properties of the SRPP
ahead of what is required in clause 4.2. The EMC requirements addressed include the discharge of electrostatic energy.
5 Requirements on bonding networks
5.1 Bonding configurations
Bonding configurations can be addressed at a building level (i.e. CBN), at an installation level (i.e. merging of CBN and
MESHed Bonding Network (MESH-BN)) and at an equipment level (i.e. MESH-BN).
Recommendation ITU-T K.27 [i.2] deals with bonding configurations of ICT equipment at a building and installation
level. Regarding the bonding configuration at an equipment level a MESH-BN is explicitly distinguished in the present
document.
5.2 CBN within a telecommunication building or data centre
Telecommunication building or data centre shall be provided with a CBN having sufficiently low impedance and high
current conducting capability to meet the general requirements of clause 4. The earthing conductor and the equipotential
bonding conductors should be coloured in accordance to international and national regulations.
The main earthing terminal of the CBN shall be extended by a bonding ring conductor along the inside perimeter of the
building, or a ring conductor, as a basic element of the CBN, shall at least comprise a system block by its outer
perimeter. A growth by extension of the telecommunication or ICT installation inside a building or a data centre
requires such a minimum CBN version to be augmented into a three dimensional grid structure, approximating a
Faraday cage (see figure 1). The impact of interfering energy in an exposed location or the need for information security
enforces the provision of shielded rooms as a maximum requirement to the CBN.
Annex A gives information about the implementation principles for the CBN, thereby following Recommendation
ITU-T K.27 [i.2], clause 4.2.1.
5.3 BN within a telecommunication or ICT system
Within a telecommunication or ICT system, especially a system block, the BN shall be of the mesh type. The
MESH-BN shall provide sufficiently low impedance and high current conducting capability to meet the general
requirements in clause 4.
The MESH-BN shall interconnect shelves, cabinets, rack rows, cable racks, ducts, troughs, distribution frames, cable
shields and bonding mat to constitute the required SRPP.
All metallic parts of the MESH-BN shall form an electrically continuous whole. This does not necessarily require
bonding by additional bonding straps, but that improvements should be taken into account when determining the
finishes and fastening methods to be used. The mechanical structure comprised by the MESH-BN shall form part of the
SRPP.
As an example, figure 2 addresses interconnections within a system block, essential to a MESH-BN. This example
follows the implementation principles for the MESH-BN outlined in Recommendation ITU-T K.27 [i.2], clause 4.2.2.
ETSI

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11 ETSI EN 300 253 V2.2.1 (2015-06)
The cable shields shall be connected to the rack.
Support column of the building
Reinforcement
Bonding ring conductor
System block 1
Mesh-BN equipment
Floor
Interconnection
Floor n+1
Bonding mat
The cable shield shall be
connected to the rack
Interconnected
xxxxxxx xxxxxxx
reinforcement
Floor n
Mesh-BN equipment
xxxxxxx xxxxxxx
System block 2
Mesh-BN equipment
Plumbing
L1 L2 L3 N PE
PE
AC distribution
Lower floor
Airco
48V DC service panel
(DC return conductor
terminal)
Frame of DC powerplant
xxxxxxxxxxxxxxx
Main earthing terminal
Basement
PE
DC return conductor (+48V)
Telecom cables
Interconnected reinforcement
xxx x
and building steel
Bonding ring conductor
(recommended)
Intra-system cabling
xx xxxxx
Shielded Inter-system cabling
Bonding conductor
To earth electrode
To foundation
reinforcement/ring conductor



Figure 1: Example of a CBN/MESH-BN installation inside a telecommunication building
or data centre
ETSI
xxx xx
x x
xxxxxxx x xx x
x xx xxxxxxx
x
xx
xxx xxx
xxx

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12 ETSI EN 300 253 V2.2.1 (2015-06)

Figure 2: Example of a CBN/MESH-BN configuration with common DC return conductor
connected to the CBN at multiple points
ETSI

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13 ETSI EN 300 253 V2.2.1 (2015-06)
5.4 Merging of CBN and MESH-BNs
All
...

Draft ETSI EN 300 253 V2.1.11 (2015-01)






EUROPEAN STANDARD
Environmental Engineering (EE);
Earthing and bonding of ICT equipment powered by -48 VDC in
telecom and data center

---------------------- Page: 1 ----------------------
2 Draft ETSI EN 300 253 V2.1.11 (2015-01)



Reference
REN/EE-0250
Keywords
bonding, earthing, equipment practice
ETSI
650 Route des Lucioles
F-06921 Sophia Antipolis Cedex - FRANCE

Tel.: +33 4 92 94 42 00  Fax: +33 4 93 65 47 16

Siret N° 348 623 562 00017 - NAF 742 C
Association à but non lucratif enregistrée à la
Sous-Préfecture de Grasse (06) N° 7803/88

Important notice
The present document can be downloaded from:
http://www.etsi.org
The present document may be made available in electronic versions and/or in print. The content of any electronic and/or
print versions of the present document shall not be modified without the prior written authorization of ETSI. In case of any
existing or perceived difference in contents between such versions and/or in print, the only prevailing document is the
print of the Portable Document Format (PDF) version kept on a specific network drive within ETSI Secretariat.
Users of the present document should be aware that the document may be subject to revision or change of status.
Information on the current status of this and other ETSI documents is available at
http://portal.etsi.org/tb/status/status.asp
If you find errors in the present document, please send your comment to one of the following services:
http://portal.etsi.org/chaircor/ETSI_support.asp
Copyright Notification
No part may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying
and microfilm except as authorized by written permission of ETSI.
The content of the PDF version shall not be modified without the written authorization of ETSI.
The copyright and the foregoing restriction extend to reproduction in all media.

© European Telecommunications Standards Institute 2015.
All rights reserved.

TM TM TM
DECT , PLUGTESTS , UMTS and the ETSI logo are Trade Marks of ETSI registered for the benefit of its Members.
TM
3GPP and LTE™ are Trade Marks of ETSI registered for the benefit of its Members and
of the 3GPP Organizational Partners.
GSM® and the GSM logo are Trade Marks registered and owned by the GSM Association.
ETSI

---------------------- Page: 2 ----------------------
3 Draft ETSI EN 300 253 V2.1.11 (2015-01)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 5
Introduction . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 7
3 Definitions and abbreviations . 7
3.1 Definitions . 7
3.1.1 IEC definitions (by IEC 60050 numbers) . 7
3.1.2 Telecommunication definitions . 8
3.2 Abbreviations . 9
4 General requirements . 10
4.1 Safety from electrical hazards . 10
4.2 Signal reference . 10
4.3 EMC performance . 10
5 Requirements on bonding networks . 10
5.1 Bonding configurations . 10
5.2 CBN within a telecommunication building or data centre . 10
5.3 BN within a telecommunication or ICT system . 11
5.4 Merging of CBN and MESH-BNs . 14
5.5 Cabling within and between BNs . 14
6 Requirements for power distribution . 14
6.1 DC power distribution of secondary supply . 14
6.2 DC power distribution of tertiary supplies . 14
6.3 AC mains distribution and bonding of the protective conductor . 15
6.4 AC power distribution from tertiary power supply . 15
Annex A (normative): Rationale about CBN co-ordination . 16
Annex B (informative): Rationale about the integration of the DC return conductor into the
merged CBN/MESH-BN . 18
Annex C (normative): AC mains distribution and bonding of the protective conductor . 20
Annex D (informative): Bibliography . 24
History . 25


ETSI

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4 Draft ETSI EN 300 253 V2.1.11 (2015-01)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://ipr.etsi.org).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This draft European Standard (EN) has been produced by ETSI Technical Committee Environmental Engineering (EE),
and is now submitted for the combined Public Enquiry and Vote phase of the ETSI standards EN Approval Procedure.
The present document has been produced within the framework of the following considerations:
a) ICT equipment is generally installed in telecommunication or data centres and held in racks, cabinets or other
mechanical structures;
b) the existing Recommendation ITU-Ts and CENELEC standards in such matters do not ensure the required
standardization at the equipment level;
c) network operators and equipment providers agreed to standardize on a bonding configuration that facilitates:
- compliance with functional requirements including Electromagnetic Compatibility (EMC) aspects of
emission and immunity;
- compatible building and equipment provisions;
- installation of new telecommunication or data centres as well as expansion or replacement of
installations in existing telecommunication or data centres with equipment coming from different
suppliers;
- a structured installation practice;
- simple maintenance rules;
- contracting on a common basis;
- cost effectiveness in development, manufacturing, installation and operation.

Proposed national transposition dates
Date of latest announcement of this EN (doa): 3 months after ETSI publication
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 6 months after doa
Date of withdrawal of any conflicting National Standard (dow): 6 months after doa

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5 Draft ETSI EN 300 253 V2.1.11 (2015-01)
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "may not", "need", "need not", "will",
"will not", "can" and "cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms
for the expression of provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
The present document addresses earthing and bonding of ICT equipment in telecommunication or data centres in
relation to safety, functional performance and EMC.
Information regarding the general principles on earthing for telecommunication or data centres has been published by
the ITU-T in the handbook on "Earthing of telecommunication installations" [i.1]. Recommendation ITU-T K.27 [i.2]
deals with bonding configurations and earthing inside a telecommunication building or data centre. One bonding
configuration only is selected from Recommendation ITU-T K.27 [i.2] (CBN/MESH-BN) and tailored to the present
document.
The author thanks the International Electrotechnical Commission (IEC) for permission to reproduce Information from
its International Standard IEC 60364-1 (CENELEC HD 60364-1 [i.11]) ed. 5.0 (2005). All such extracts are copyright
of IEC, Geneva, Switzerland. All rights reserved. Further information on the IEC is available from www.iec.ch. IEC has
no responsibility for theplacement and context in which the extracts and contents are reproduced by the author, nor is
IEC in any wayresponsible for the other content or accuracy therein.
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6 Draft ETSI EN 300 253 V2.1.11 (2015-01)
1 Scope
The present document applies to earthing and bonding of ICT equipment operating with DC voltage defined in
ETSI EN 300 132-2 [i.9], in order to facilitate the installation, operation and maintenance of equipment.
It also co-ordinates with the pre-conditions of the installation to achieve the following targets:
- safety from electrical hazards;
- reliable signal reference;
- satisfactory Electromagnetic Compatibility (EMC) performance.
The specification of ICT equipment and of the pre-conditions of installation are subject to agreement of the parties (e.g.
the supplier and the purchaser) and the procedure to achieve agreement is covered by annex A of the present document.
The present document does not cover safety and EMC aspects of the equipment. Those aspects are covered by other
relevant standards.
The present document does not apply to the installation of ICT equipment in locations other than telecommunication
and data centres, e.g. ICT equipment within a customer's building, including subscriber line termination.
NOTE: Earthing and bonding of equipment installed in locations other than telecommunication and data centres
is covered by CENELEC EN 50310 [i.6].
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] CENELEC HD 60364-4-41: "Low-voltage electrical installations - Part 4-41: Protection for safety
- Protection against electric shock".
[2] CENELEC HD 60364-5-54: "Low-voltage electrical installations - Part 5-54: Selection and
erection of electrical equipment - Earthing arrangements, protective conductors and protective
bonding conductors".
[3] CENELEC EN 60950-1: "Information technology equipment - Safety - Part 1: General
requirements".
[4] CENELEC EN 41003: "Particular safety requirements for equipment to be connected to
telecommunication networks and/or a cable distribution system".
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7 Draft ETSI EN 300 253 V2.1.11 (2015-01)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ITU-T handbook: "Earthing of telecommunication installations".
[i.2] Recommendation ITU-T K.27 (1991): "Bonding Configurations and Earthing inside a
Telecommunication Building".
[i.3] IEC 60050: "International Electrotechnical Vocabulary".
[i.4] IEC 60050-604: "International Electrotechnical Vocabulary. Chapter 604: Generation,
transmission and distribution of electricity - Operation".
[i.5] IEC 60050-826: "International Electrotechnical Vocabulary. Electrical installations of buildings".
[i.6] CENELEC EN 50310: "Application of equipotential bonding and earthing in buildings with
information technology equipment".
[i.7] CENELEC EN 62305 series: "Protection against lightning".
[i.8] IEC 60050-195: "International Electrotechnical Vocabulary. Electrical installations of buildings".
Earthing and protection against electric shock.
[i.9] ETSI EN 300 132-2: "Environmental Engineering (EE); Power supply interface at the input to
telecommunications and datacom (ICT) equipment; Part 2: Operated by -48 V direct current (dc)".
[i.10] CENELEC EN 50162: "Protection against corrosion by stray current from d.c. system".
[i.11] CENELEC HD 60364-1: "Electrical installation of buildings; Part 1: Scope, object and
definitions".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply.
The following definitions with respect to earthing and bonding are introduced by the IEC 60050 [i.3] and are used
within the present document to maintain conformity.
3.1.1 IEC definitions (by IEC 60050 numbers)
NOTE: IEC 60050 [i.3] references are given in parentheses (see IEC 60050-604 [i.4], IEC 60050-826 [i.5] and
IEC 60050-195 [i.8]).
earth (195-01-03): part of the Earth which is in electric contact with an earth electrode and the electric potential of
which is not necessarily equal to zero earthing arrangement
earthing conductor (195-02-03): conductor which provides a conductive path, or part of the conductive path, between
a given point in a system or in an installation or in equipment and an earth electrode
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8 Draft ETSI EN 300 253 V2.1.11 (2015-01)
earth electrode (195-02-01): conductive part, which may be embedded in a specific conductive medium, e.g. concrete
or coke, in electric contact with the Earth
earthing network (604-04-07): part of an earthing installation that is restricted to the earth electrodes and their
interconnections
equipotential bonding (195-01-10): provision of electric connections between conductive parts, intended to achieve
equipotentiality
main earthing terminal (826-13-15): terminal or busbar which is part of the earthing arrangement of an installation
and enabling the electric connection of a number of conductors for earthing purposes
Neutral conductor (N) (826-01-03): conductor connected to the neutral point of a system and capable of contributing
to the transmission of electrical energy
PEN conductor (826-13-25): conductor combining the functions of both a protective earthing conductor and a neutral
conductor
protective earthing conductor (PE) (826-13-23): protective conductor provided for protective earthing
IT, TN-C, TN-S, and TT systems (see HD 60 364-1: The codes used have the following meanings:
First letter – Relationship of the power system to earth:
T = direct connection of one point to earth;
I = all live parts isolated from earth, or one point connected to earth through a high impedance.
Second letter – Relationship of the exposed-conductive-parts of the installation to earth:
T = direct electrical connection of exposed-conductive-parts to earth, independently of the earthing of any point of the
power system;
N = direct electrical connection of the exposed-conductive-parts to the earthed point of the power system
Subsequent letter(s) (if any) – Arrangement of neutral and protective conductors:
S = protective function provided by a conductor separate from the neutral conductor or from the earthed line conductor.
C = neutral and protective functions combined in a single conductor (PEN conductor).
3.1.2 Telecommunication definitions
The following definitions, specific to telecommunication or data centre installations and not covered by the
IEC 60050 [i.3], are used within the present document. Correspondence to Recommendation ITU-T K.27 [i.2] is
indicated as appropriate.
bonding mat: essential means to provide a SRPP by a discernible, nearly regular mesh structure
NOTE: The bonding mat may be located either below or above a collection of equipment constituting a system
block.
Bonding Network (BN), (Recommendation ITU-T K.27 [i.2]): set of interconnected conductive structures that
provides an "electromagnetic shield" for electronic systems and personnel at frequencies from Direct Current (DC) to
low Radio Frequency (RF)
NOTE: The term "electromagnetic shield" denotes any structure used to divert, block or impede the passage of
electromagnetic energy. In general, a BN need not be connected to earth but all BNs considered in the
present document will have an earth connection.
Common Bonding Network (CBN), (Recommendation ITU-T K.27 [i.2]): principal means for effective bonding and
earthing inside a telecommunication building or data centre
NOTE: It is the set of metallic components that are intentionally or incidentally interconnected to form the
principal BN in a building. These components include: structural steel or reinforcing rods, metallic
plumbing, Alternating Current (AC) power conduit, PE conductors, cable racks and bonding conductors.
The CBN always has a mesh topology and is connected to the earthing network.
DC return conductor: (+) conductor of the -48 V or -60 V secondary DC supply
ICT equipment: equipment designed for Information and Communication Technologies
NOTE: It is similar to Information Technology (IT), but focuses primarily on communication technologies. This
includes the Internet, wireless networks, cell phones, and other communication mediums.
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9 Draft ETSI EN 300 253 V2.1.11 (2015-01)
MESHed Bonding Network (MESH-BN), (Recommendation ITU-T K.27 [i.2]): bonding network in which all
associated equipment frames, racks and cabinets and usually the DC power return conductor, are bonded together as
well as at multiple points to the CBN
NOTE 1: Consequently, the MESH-BN augments the CBN.
NOTE 2: See figure 1 of the present document.
MESHed Isolated Bonding Network (MESH-IBN), (Recommendation ITU-T K.27 [i.2]): type of IBN in which the
components of the IBN (e.g. equipment frames) are interconnected to form a mesh-like structure
NOTE: This may, for example, be achieved by multiple interconnections between cabinet rows, or by connecting
all equipment frames to a metallic grid (a "bonding mat") extending beneath the equipment. The bonding
mat is, of course, insulated from the adjacent CBN. If necessary the bonding mat could include vertical
extensions, resulting in an approximation to a Faraday cage. The spacing of the grid is chosen according
to the frequency range of the electromagnetic environment.
power supply:
- primary supply: public mains or, under emergency conditions, a locally generated AC supply
- secondary supply: supply to the ICT equipment, racks or system block, derived from the primary supply
- tertiary supplies: supplies to the ICT equipment, derived from the secondary supply
system: regularly interacting or interdependent group of items forming a unified whole
system block: functional group of equipment depending in its operation and performance on its connection to the same
system reference potential plane, inherent to a MESH-BN
System Reference Potential Plane (SRPP): conductive solid plane, as an ideal goal in potential equalizing, is
approached in practice by horizontal or vertical meshes
NOTE 1: The mesh width thereof is adapted to the frequency range to be considered. Horizontal and vertical
meshes may be interconnected to form a grid structure approximating to a Faraday cage.
NOTE 2: The SRPP facilitates signalling with reference to a common potential.
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
AC Alternating Current
BN Bonding Network
CBN Common Bonding Network
DC Direct Current
EMC ElectroMagnetic Compatibility
LPS Lightning Protection System
MESH-BN MESHed Bonding Network
MESH-IBN MESHed Isolated Bonding Network
N Neutral conductor
PE Protective Earth conductor
PEN combined Protective Earth and Neutral conductor
RF Radio Frequency
SRPP System Reference Potential Plane
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10 Draft ETSI EN 300 253 V2.1.11 (2015-01)
4 General requirements
4.1 Safety from electrical hazards
To achieve safety the standards EN 60950-1 [3], EN 41003 [4] and CENELEC HD 60364-4-41 [1] shall be applied in
the design of the equipment. The installation of PEs and equipotential bonding conductors shall be carried out in
accordance with CENELEC HD 60364-5-54 [2].
The conductors involved shall provide sufficiently high current conducting capability and low impedance according to
the relevant safety standards to avoid electric shock, risk of fire, or damage to the equipment under normal or faulty
operating conditions within an equipment or the distribution network, or due to the impact of induced voltage and
current, e.g. by lightning.
4.2 Signal reference
Reliable signal reference shall be provided by a SRPP dedicated at least to a functional unit or a system block. To avoid
undue functional distortion or risk of component failure, the SRPP shall provide sufficiently low impedance up to the
highest frequency to be regarded by using a metal plane or a meshed configuration having adequate mesh dimensions,
e.g. a bonding mat. The frequency band to be covered shall include the spectral components of transients caused by
switching, short circuits and atmospheric discharges.
NOTE: Signal reference to the SRPP does not always imply signal return via the SRPP.
4.3 EMC performance
Measures to gain a satisfactory EMC performance shall be assisted by a SRPP. The SRPP shall provide sufficiently low
impedance for efficient connection of filters, cabinets and cable shields. The requirement to avoid undue emission of, or
susceptibility to electromagnetic energy under normal operating conditions may govern the properties of the SRPP
ahead of what is required in clause 4.2. The EMC requirements addressed include the discharge of electrostatic energy.
5 Requirements on bonding networks
5.1 Bonding configurations
Bonding configurations can be addressed at a building level (i.e. CBN), at an installation level (i.e. merging of CBN and
MESHed Bonding Network (MESH-BN)) and at an equipment level (i.e. MESH-BN).
Recommendation ITU-T K.27 [i.2] deals with bonding configurations of ICT equipment at a building and installation
level. Regarding the bonding configuration at an equipment level a MESH-BN is explicitly distinguished in the present
document.
5.2 CBN within a telecommunication building or data centre
Telecommunication building or data centre shall be provided with a CBN having sufficiently low impedance and high
current conducting capability to meet the general requirements of clause 4. The earthing conductor and the equipotential
bonding conductors should be coloured in accordance to international and national regulations.
The main earthing terminal of the CBN shall be extended by a bonding ring conductor along the inside perimeter of the
building, or a ring conductor, as a basic element of the CBN, shall at least comprise a system block by its outer
perimeter. A growth by extension of the telecommunication or ICT installation inside a building or a data centre
requires such a minimum CBN version to be augmented into a three dimensional grid structure, approximating a
Faraday cage (see figure 1). The impact of interfering energy in an exposed location or the need for information security
enforces the provision of shielded rooms as a maximum requirement to the CBN.
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11 Draft ETSI EN 300 253 V2.1.11 (2015-01)
Annex A gives information about the implementation principles for the CBN, thereby following
Recommendation ITU-T K.27 [i.2], clause 4.2.1.
5.3 BN within a telecommunication or ICT system
Within a telecommunication or ICT system, especially a system block, the BN shall be of the mesh type. The
MESH-BN shall provide sufficiently low impedance and high current conducting capability to meet the general
requirements in clause 4.
The MESH-BN shall interconnect shelves, cabinets, rack rows, cable racks, ducts, troughs, distribution frames, cable
shields and bonding mat to constitute the required SRPP.
All metallic parts of the MESH-BN shall form an electrically continuous whole. This does not necessarily require
bonding by additional bonding straps, but that improvements should be taken into account when determining the
finishes and fastening methods to be used. The mechanical structure comprised by the MESH-BN shall form part of the
SRPP.
As an example, figure 2 addresses interconnections within a system block, essential to a MESH-BN. This example
follows the implementation principles for the MESH-BN outlined in Recommendation ITU-T K.27 [i.2], clause 4.2.2.
The cable shields shall be connected to the rack.
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12 Draft ETSI EN 300 253 V2.1.11 (2015-01)
Support column of the building
Reinforcement
Bonding ring conductor
System block 1
Mesh-BN equipment
Floor
Interconnection
Floor n+1
Bonding mat
The cable shield shall be
connected to the rack
Interconnected
xxxxxxx xxxxxxx
reinforcement
Floor n
Mesh-BN equipment
xxxxxxx
xxxxxxx
System block 2
Mesh-BN equipment
Plumbing
L1 L2 L3 N PE
PE
AC distribution
Lower floor
A rco
i
48V DC service panel
(DC return conductor
terminal)
Frame of DC powerplant
xxxxxxxxxxxxxxx
Main earthing terminal
Basement
PE
DC return conductor (+48V)
Telecom cables
Interconnected reinforcement
xxx x
and building steel
Bonding ring conductor
(recommended)
Intra-system cabling
xxx
xx xx
Shielded Inter-system cabling
Bonding conductor
To earth electrode To foundation
reinforcement/ring conductor


Figure 1: Example of a CBN/MESH-BN installation inside a telecommunication building
or data centre
ETSI
xxx xx
x x
xxxxxxx x xx x
x xx xxxxxxx
x
xx
xxx xxx
xxx

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