SIST ETS 300 253 E1:2006
(Main)Equipment Engineering (EE); Earthing and bonding of telecommunication equipment in telecommunication centres
- Abstract
This European Telecommunication Standard (ETS) applies in telecommunication centres and similar installations to the bonding network of the building, the bonding network of the equipment, and the interconnection between these two networks. It contributes to the standardization of telecommunication equipment and co-ordinates with the pre-requirements of installation conditions to achieve the following targets:
- safety from electrical hazards;
- reliable signal reference;
- satisfactory Electromagnetic Compatibility (EMC) performance.
A defined bonding configuration down to the equipment level shall facilitate the installation, operation and maintenance of telecommunication centres in telecommunication buildings or similar installations independent of the equipment supplier. The specification of telecommunication equipment and of the pre-requirements of installation are subject to agreement of the parties (e.g. the supplier and the purchaser). Annex A can be used in the procedure to achieve agreement. This ETS does not apply to telecommunication equipment not intended to be installed inside telecommunication centres, e.g.:
- smaller telecommunication equipment inside a subscriber's building;
- subscriber line terminal equipment.
NOTE: A separate ETS about earthing and bonding of telecommunication equipment inside a subscriber's building is under consideration.
- Status
- Published
- Publication Date
- 31-Jan-2006
- Current Stage
- 6060 - National Implementation/Publication (Adopted Project)
- Start Date
- 01-Feb-2006
- Due Date
- 01-Feb-2006
- Completion Date
- 01-Feb-2006
SIST ETS 300 253 E1:2006 is the Slovenian adoption of ETS 300 253 Edition 1, a European Telecommunication Standard from ETSI. It specifies earthing and bonding for telecommunication equipment in telecommunication centres and similar installations, so that equipment suppliers, purchasers, installers, and operators can work to the same bonding configuration.
What does SIST ETS 300 253 E1:2006 specify?
SIST ETS 300 253 E1:2006 applies to the building bonding network, the equipment bonding network, and the connection between them in telecommunication centres and similar installations. Its purpose is to coordinate installation conditions and equipment design so the installation supports electrical safety, a reliable signal reference, and satisfactory EMC performance.
The document is organized into six clauses and three annexes.
| Annex | What it covers |
|---|---|
| Annex A | Normative rationale about CBN co-ordination |
| Annex B | Informative rationale about integrating the DC return conductor into the merged CBN/MESH-BN |
| Annex C | Informative bibliography |
The scope also makes clear that the standard is for telecommunication centres, not for smaller telecommunication equipment inside a subscriber's building or for subscriber line terminal equipment. In practice, that means the document is aimed at centralized telecom rooms, racks, cabinets, and building-wide bonding arrangements rather than end-user premises equipment.
What are the key requirements of SIST ETS 300 253 E1:2006?
Clause 4 - safety, signal reference, and EMC
SIST ETS 300 253 E1:2006 requires the installation and equipment design to support three linked outcomes: safety from electrical hazards, stable signal reference, and EMC performance. Clause 4 ties those goals to low-impedance, high-current-capability conductors and to recognized safety standards for equipment and building installation.
For safety, the document points to EN 60950, EN 41003, and CENELEC HD 384.4.41 for equipment and shock protection, and to CENELEC HD 384.5.54 for protective conductors and equipotential bonding. In practice, this means the bonding paths must be able to carry fault and induced currents without creating shock, fire, or equipment-damage risks.
Clause 4 also introduces the system reference potential plane (SRPP) as the basis for signal reference. The SRPP must have sufficiently low impedance up to the relevant highest frequencies, including transients from switching, short circuits, and atmospheric discharges, so signalling and control circuits see a common reference point.
For EMC, the SRPP is also the means for connecting filters, cabinets, and cable shields effectively. The standard expects the bonding layout to reduce emissions and susceptibility, including electrostatic discharge effects.
Clause 5 - building bonding, system bonding, and cabling
SIST ETS 300 253 E1:2006 distinguishes between the Common Bonding Network (CBN) at building level and the Meshed Bonding Network (MESH-BN) at system level. Clause 5 says the CBN is the building-wide principal bonding and earthing network, while the MESH-BN is the mesh used within a telecommunication system or system block.
Each telecommunication building shall have a CBN with sufficiently low impedance and adequate current-carrying capacity. The CBN is built around a main earthing terminal and a ring conductor, and it may develop into a three-dimensional grid approaching a Faraday cage as the installation grows. In practice, this is what gives the building a stable bonding backbone.
Within a telecommunication system, the BN shall be mesh type. Clause 5 requires the MESH-BN to interconnect shelves, cabinets, rack rows, cable racks, ducts, troughs, distribution frames, cable shields, and bonding mats so they all contribute to the SRPP. The practical effect is that the equipment structure itself becomes part of the bonding path, not an afterthought.
Clause 5.4 requires all BNs of telecommunication systems, and their associated DC return conductors, to be connected to the CBN. The MESH-BN augments the CBN through multiple interconnections to the main earthing terminal, which matters because it keeps the whole installation at a more uniform potential.
Clause 5.5 controls cabling inside and between BNs. Power and signal cables should run close to the augmented CBN members, AC mains cables and signal cables need separation unless shielding is adequate, and cable shields are to be bonded directly to racks, cabinets, or the SRPP at each end. In practice, this reduces coupling, improves EMC, and simplifies maintenance because shield terminations are defined.
Clause 6 - DC and AC power distribution
SIST ETS 300 253 E1:2006 sets specific bonding rules for secondary DC supply. The positive and negative conductors should be routed close together, and each DC return conductor must be bonded to the CBN and to at least one point of the SRPP. The document also requires the DC return path to be designed for less than 1 V voltage drop and to withstand overcurrent during faults.
For tertiary DC supplies, the reference potential terminal shall be connected to the MESH-BN. That keeps local low-voltage supplies tied into the same reference structure as the rest of the system block.
For AC mains inside a telecommunication building, the standard requires a TN-S arrangement, with no PEN conductor within the building. Depending on the outdoor supply arrangement, the indoor installation must follow the stated TN-S, TN-C, TT, or IT transition rules, with the PE and N conductors treated according to the network type. This matters because the building earthing arrangement has to be coordinated with the upstream distribution network rather than improvised locally.
What terms does SIST ETS 300 253 E1:2006 define?
- Bonding Network (BN) - A set of interconnected conductive structures that acts as an electromagnetic shield for equipment and personnel from DC to low RF.
- Common Bonding Network (CBN) - The main bonding and earthing network inside a telecommunication building, formed by metallic parts intentionally or incidentally interconnected in a mesh topology.
- Meshed Bonding Network (MESH-BN) - A mesh bonding network that interconnects equipment frames, racks, and usually the DC return conductor at multiple points to the CBN.
- Meshed Isolated Bonding Network (MESH-IBN) - A mesh-like isolated bonding network whose components are interconnected but insulated from the CBN.
- System Reference Potential Plane (SRPP) - The conductive reference plane used for signalling and potential equalization, approximated in practice by meshes or bonding mats.
- Protective conductor (PE) - A conductor used to connect exposed and extraneous conductive parts to the earthing arrangement for shock protection.
- PEN conductor - An earthed conductor that combines the functions of protective conductor and neutral conductor.
- DC return conductor - The (+) conductor of the -48 V or -60 V secondary DC supply.
Who uses SIST ETS 300 253 E1:2006?
SIST ETS 300 253 E1:2006 is used by telecommunication equipment suppliers, building designers, installation contractors, network operators, and maintenance teams working in telecommunication centres. It is also relevant to purchasers and quality managers who need to agree the installation pre-requirements and the bonding configuration before equipment is supplied or installed.
In practice, these users apply the standard when planning racks, cabinets, cable routes, earthing terminals, DC power distribution, and shield bonding. It is especially relevant where equipment from different suppliers must work together in the same building or system block.
Which standards are used with SIST ETS 300 253 E1:2006?
Clause 2 and the annexes rely on several related standards and publications:
- CENELEC HD 384.4.41 - protection against electric shock for building installations.
- CENELEC HD 384.5.54 - earthing arrangements and protective conductors.
- CENELEC EN 60950 - safety of information technology equipment, used for equipment-level safety design.
- CENELEC EN 41003 - particular safety requirements for telecommunication network connection.
- IEC 50, IEC 50 (604), IEC 50 (826) - the vocabulary used for earthing, electrical installations, and related definitions.
- CCITT Recommendation K.27 - the main basis for the bonding configuration concepts used in the document.
- ETS 300 132-1 and ETS 300 132-2 - AC and DC power supply interfaces at telecommunication equipment inputs.
- IEC 364 / IEC 364-3 / IEC 364-5-54 - building electrical installation concepts, including TN-S, TN-C, TT, and earthing arrangements.
These references provide the safety terminology, power-system categories, and bonding concepts that the standard builds on.
What does the SIST ETS 300 253 E1:2006 document contain?
The document includes clauses for scope, normative references, abbreviations and definitions, general requirements, bonding networks, and power distribution. It also includes four figures showing a CBN/MESH-BN installation, a system block arrangement, and the transition between outdoor and indoor mains supply modes.
Annex A gives the rationale for CBN co-ordination, including how building structure, lightning protection, and mains supply arrangements support the bonding strategy. Annex B explains why the DC return conductor should normally be integrated into the merged CBN/MESH-BN and what to consider when existing installations have to stay unchanged. Annex C lists background publications for further technical context.
For design work, the document is mainly about how to build the earthing and bonding architecture. For installation and maintenance, it shows how to route cables, bond shields, connect DC returns, and align the indoor mains system with the upstream supply arrangement.
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Frequently Asked Questions
SIST ETS 300 253 E1:2006 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Equipment Engineering (EE); Earthing and bonding of telecommunication equipment in telecommunication centres". This standard covers: This European Telecommunication Standard (ETS) applies in telecommunication centres and similar installations to the bonding network of the building, the bonding network of the equipment, and the interconnection between these two networks. It contributes to the standardization of telecommunication equipment and co-ordinates with the pre-requirements of installation conditions to achieve the following targets: - safety from electrical hazards; - reliable signal reference; - satisfactory Electromagnetic Compatibility (EMC) performance. A defined bonding configuration down to the equipment level shall facilitate the installation, operation and maintenance of telecommunication centres in telecommunication buildings or similar installations independent of the equipment supplier. The specification of telecommunication equipment and of the pre-requirements of installation are subject to agreement of the parties (e.g. the supplier and the purchaser). Annex A can be used in the procedure to achieve agreement. This ETS does not apply to telecommunication equipment not intended to be installed inside telecommunication centres, e.g.: - smaller telecommunication equipment inside a subscriber's building; - subscriber line terminal equipment. NOTE: A separate ETS about earthing and bonding of telecommunication equipment inside a subscriber's building is under consideration.
This European Telecommunication Standard (ETS) applies in telecommunication centres and similar installations to the bonding network of the building, the bonding network of the equipment, and the interconnection between these two networks. It contributes to the standardization of telecommunication equipment and co-ordinates with the pre-requirements of installation conditions to achieve the following targets: - safety from electrical hazards; - reliable signal reference; - satisfactory Electromagnetic Compatibility (EMC) performance. A defined bonding configuration down to the equipment level shall facilitate the installation, operation and maintenance of telecommunication centres in telecommunication buildings or similar installations independent of the equipment supplier. The specification of telecommunication equipment and of the pre-requirements of installation are subject to agreement of the parties (e.g. the supplier and the purchaser). Annex A can be used in the procedure to achieve agreement. This ETS does not apply to telecommunication equipment not intended to be installed inside telecommunication centres, e.g.: - smaller telecommunication equipment inside a subscriber's building; - subscriber line terminal equipment. NOTE: A separate ETS about earthing and bonding of telecommunication equipment inside a subscriber's building is under consideration.
SIST ETS 300 253 E1:2006 is classified under the following ICS (International Classification for Standards) categories: 33.050.01 - Telecommunication terminal equipment in general. The ICS classification helps identify the subject area and facilitates finding related standards.
SIST ETS 300 253 E1:2006 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
01-februar-2006
Inženiring opreme (EE) – Ozemljitev in povezave telekomunikacijske opreme v
telekomunikacijskih centrih
Equipment Engineering (EE); Earthing and bonding of telecommunication equipment in
telecommunication centres
Ta slovenski standard je istoveten z: ETS 300 253 Edition 1
ICS:
33.050.01 Telekomunikacijska Telecommunication terminal
terminalska oprema na equipment in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN ETS 300 253
TELECOMMUNICATION January 1995
STANDARD
Source: ETSI TC-EE Reference: DE/EE-02002
ICS: 33.080
Equipment, earthing, bonding
Key words:
Equipment Engineering (EE);
Earthing and bonding of telecommunication equipment
in telecommunication centres
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
F-06921 Sophia Antipolis CEDEX - FRANCE
Postal address:
650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Office address:
c=fr, a=atlas, p=etsi, s=secretariat - secretariat@etsi.fr
X.400: Internet:
Tel.: +33 92 94 42 00 - Fax: +33 93 65 47 16
Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1995. All rights reserved.
New presentation - see History box
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ETS 300 253: January 1995
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Editing and Committee Support Dept." at the address shown on the title page.
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ETS 300 253: January 1995
Contents
Foreword .5
Introduction.5
1 Scope .7
2 Normative references.7
3 Abbreviations and definitions .8
3.1 Abbreviations .8
3.2 Definitions .8
3.2.1 IEC definitions (by IEC 50 numbers).8
3.2.2 Telecommunication definitions.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.11
5.3 BN within a telecommunication 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.18
Annex B (informative): Rationale about the integration of the DC return conductor into the merged
CBN/MESH-BN .20
Annex C (informative): Bibliography.21
History.22
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ETS 300 253: January 1995
Blank page
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ETS 300 253: January 1995
Foreword
This European Telecommunication Standard (ETS) has been produced by the Equipment Engineering
(EE) Technical Committee of the European Telecommunications Standards Institute (ETSI).
This ETS has been produced within the framework of the following considerations:
a) centralized telecommunication equipment is generally installed in telecommunication centres and
held in racks, cabinets or other mechanical structures;
b) the existing CCITT and CCIR Recommendations 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 centres as well as expansion or replacement of
installations in existing telecommunication 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.
Transposition dates
Date of latest announcement of this ETS (doa): 30 April 1995
Date of latest publication of new National Standard 31 October 1995
or endorsement of this ETS (dop/e):
Date of withdrawal of any conflicting National Standard (dow): 31 October 1995
Introduction
This ETS addresses earthing and bonding of telecommunication equipment in telecommunication centres
in relation to safety, functional performance and EMC.
Information regarding the general principles on earthing for telecommunication sites has been published
by the CCITT in the handbook on "Earthing of telecommunication installations" (see annex C). CCITT
Recommendation K.27 deals with bonding configurations and earthing inside a telecommunication
building. One bonding configuration only is selected from CCITT Recommendation K.27 and tailored to
this ETS.
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ETS 300 253: January 1995
Blank page
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ETS 300 253: January 1995
1 Scope
This European Telecommunication Standard (ETS) applies in telecommunication centres and similar
installations to the bonding network of the building, the bonding network of the equipment, and the
interconnection between these two networks. It contributes to the standardization of telecommunication
equipment and co-ordinates with the pre-requirements of installation conditions to achieve the following
targets:
- safety from electrical hazards;
- reliable signal reference;
- satisfactory Electromagnetic Compatibility (EMC) performance.
A defined bonding configuration down to the equipment level shall facilitate the installation, operation and
maintenance of telecommunication centres in telecommunication buildings or similar installations
independent of the equipment supplier.
The specification of telecommunication equipment and of the pre-requirements of installation are subject
to agreement of the parties (e.g. the supplier and the purchaser). Annex A can be used in the procedure
to achieve agreement.
This ETS does not apply to telecommunication equipment not intended to be installed inside
telecommunication centres, e.g.:
- smaller telecommunication equipment inside a subscriber's building;
- subscriber line terminal equipment.
NOTE: A separate ETS about earthing and bonding of telecommunication equipment inside a
subscriber's building is under consideration.
2 Normative references
This ETS incorporates by dated and undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest
edition of the publication referred to applies.
[1] CENELEC HD 384.4.41: "Electrical installation of buildings; Part 4: Protection for
safety; Chapter 41: Protection against electric shock".
[2] CENELEC HD 384.5.54: "Electrical installation of buildings; Part 5: Selection
and erection of electrical equipment; Chapter 54: Earthing arrangements and
protective conductors".
[3] CENELEC EN 60950: "Safety of information technology equipment including
electrical business equipment" (as correspondent to IEC 950).
[4] CENELEC EN 41003: "Particular safety requirements for equipment to be
connected to telecommunication networks".
[5] IEC 50: "International Electrotechnical Vocabulary".
[6] IEC 50 (604): "International Electrotechnical Vocabulary; Chapter
604: Generation, transmission and distribution of electricity - Operation".
[7] IEC 50 (826): "International Electrotechnical Vocabulary; Chapter 826: Electrical
installations of buildings".
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ETS 300 253: January 1995
3 Abbreviations and definitions
3.1 Abbreviations
For the purposes of this ETS, 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 conductor
PEN combined Protective conductor and Neutral conductor
RF Radio Frequency
SRPP System Reference Potential Plane
3.2 Definitions
The following definitions with respect to earthing and bonding are introduced by the IEC 50 [5] and are
used within this ETS to maintain conformity.
3.2.1 IEC definitions (by IEC 50 numbers)
NOTE: IEC 50 [5] references are given in parentheses (see IEC 50 (604) [6] and
IEC 50 (826) [7]).
earth (826-04-01): The conductive mass of earth, whose electric potential at any point is conventionally
taken as equal to zero.
earth electrode (826-04-02): A conductive part or a group of conductive parts in intimate contact with and
providing an electrical connection with earth.
earthing network (604-04-07): The part of an earthing installation that is restricted to the earth electrodes
and their interconnections.
earthing conductor (826-04-07): A protective conductor connecting the main earthing terminal or bar to
the earth electrode.
main earthing terminal (826-04-08): A terminal or bar provided for the connection of protective
conductors, including equipotential bonding conductors and conductors for functional earthing if any, to
the means of earthing.
equipotential bonding (826-04-09): Electrical connection putting various exposed conductive parts and
extraneous conductive parts at a substantially equal potential.
equipotential bonding conductor (826-04-10): A protective conductor for ensuring equipotential
bonding.
Protective conductor (PE) (826-04-05): A conductor required by some measures for protection against
electric shock by electrically connecting any of the following parts:
- exposed conductive parts;
- extraneous conductive parts;
- main earthing terminal;
- earth electrode;
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ETS 300 253: January 1995
- earthed point of the source or artificial neutral.
Neutral conductor (N) (826-01-03): A conductor connected to the neutral point of a system and capable
of contributing to the transmission of electrical energy.
PEN conductor (826-04-06): An earthed conductor combining the functions of both protective conductor
and neutral conductor.
IT: See IEC Standard 364-3.
TN-C: See IEC Standard 364-3.
TN-S: See IEC Standard 364-3.
TT: See IEC Standard 364-3.
3.2.2 Telecommunication definitions
The following definitions, specific to telecommunication installations and not covered by the IEC 50 [5], are
used within this ETS. Correspondence to CCITT Recommendation K.27 (see annex C) is indicated as
appropriate.
Bonding Network (BN), (CCITT Recommendation K.27): A 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). 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 this ETS will have an earth connection.
Common Bonding Network (CBN), (CCITT Recommendation K.27): The CBN is the principal means
for effective bonding and earthing inside a telecommunication building. 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.
Meshed Bonding Network (MESH-BN), (CCITT Recommendation K.27): A 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. Consequently, the MESH-BN augments the
CBN (see figure 1).
Meshed Isolated Bonding Network (MESH-IBN), (CCITT Recommendation K.27): A type of IBN in
which the components of the IBN (e.g. equipment frames) are interconnected to form a mesh-like
structure. 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.
system: A regularly interacting or interdependent group of items forming a unified whole.
system block: A 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): A conductive solid plane, as an ideal goal in potential
equalising, is approached in practice by horizontal or vertical meshes. 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.
The SRPP facilitates signalling with reference to a common potential.
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ETS 300 253: January 1995
bonding mat: Essential means to provide a SRPP by a discernible, nearly regular mesh structure. The
bonding mat may be located either below or above a collection of equipment constituting a system block.
power supply:
- primary supply: The public mains or, under emergency conditions, a locally generated AC supply;
- secondary supply: The supply to the telecommunication equipment, racks or system block,
derived from the primary supply;
- tertiary supplies: The supplies to the telecommunication equipment, derived from the secondary
supply.
DC return conductor: The (+) conductor of the -48 V or -60 V secondary DC supply.
4 General requirements
4.1 Safety from electrical hazards
To achieve safety it is required to design equipment to the standards EN 60950 [3], EN 41003 [4] and
CENELEC HD 384.4.41 [1] and to perform the installation of PEs and equipotential bonding conductors,
according to CENELEC HD 384.5.54 [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 subclause 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).
CCITT Recommendation K.27 deals with bonding configurations of telecommunication equipment at a
building and installation level. Regarding the bonding configuration at an equipment level a MESH-BN is
explicitly distinguished in this ETS.
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ETS 300 253: January 1995
5.2 CBN within a telecommunication building
Each telecommunication building shall be provided with a CBN having sufficiently low impedance and high
current conducting capability to meet the general requirements of clause 4. Equipotential bonding
conductors shall be used (see IEC publication 364-5-54, section 547.1.2).
T
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