EN 62305-4:2011

Protection against lightning - Part 4: Electrical and electronic systems within structures

IEC 62305-4:2010(E) provides information for the design, installation, inspection, maintenance and testing of electrical and electronic system protection (LPM) to reduce the risk of permanent failures due to lightning electromagnetic impulse (LEMP) within a structure. This second edition cancels and replaces the first edition, published in 2006, and constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: 1) Isolating interfaces capable of reducing conducted surges on lines entering the structure are introduced. 2) Minimum cross-sections for bonding components are slightly modified. 3) First negative impulse current is introduced for calculation purposes as electromagnetic source of harm to the internal systems. 4) Selection of SPD with regard to voltage protection level is improved to take into account oscillation and induction phenomena in the circuit downstream of SPD. 5) Annex C dealing with SPD coordination is withdrawn and referred back to SC 37A. 6) A new informative Annex D is introduced giving information on factors to be considered in the selection of SPDs.

Blitzschutz --Teil 4: Elektrische und elektronische Systeme in baulichen Anlagen

Protection contre la foudre - Partie 4: Réseaux de puissance et de communication dans les structures

La CEI 62305-4:2010 fournit des informations relatives à la conception, à l'installation, à l'inspection, à la maintenance et aux essais d'une installation de protection de réseau de puissance et de communication (MPF) visant à réduire le risque de défaillances permanentes dû aux impulsions électromagnétiques de foudre (IEMF) dans une structure. Cette seconde édition annule et remplace la première édition, publiée en 2006, dont elle constitue une révision technique. La présente édition comprend les modifications techniques importantes suivantes par rapport à la précédente édition: 1) Introduction d'interfaces d'isolement capables de réduire les chocs conduits sur les services pénétrant dans la structure. 2) Légère modification des sections minimales des composants de liaison. 3) Introduction d'un premier courant pulsé négatif à des fins de calcul, comme source électromagnétique de dégradation des réseaux internes. 4) Amélioration du choix du parafoudre par rapport au niveau de protection contre les surtensions, afin de tenir compte de l'existence de phénomènes d'oscillation et d'induction dans le circuit en aval du parafoudre. 5) Suppression de l'Annexe C traitant de la coordination des parafoudres avec renvoi au SC 37A. 6) Introduction d'une nouvelle Annexe informative D fournissant des informations sur les facteurs à prendre en compte dans le choix des parafoudres. La présente version bilingue (2012-06) correspond à la version anglaise monolingue publiée en 2010-12.

Zaščita pred delovanjem strele - 4. del: Električni in elektronski sistemi v zgradbah (IEC 62305-4:2010, spremenjen)

Ta mednarodni standard zagotavlja informacije za projektiranje, namestitev, nadzor, vzdrževanje in preskušanje zaščite električnih in elektronskih sistemov (ESP) in ukrepov za zmanjšanje tveganja za trajne okvare zaradi elektromagnetnih impulzov strele (LEMP) v zgradbi. Ne zajema zaščite pred elektromagnetnimi motnjami zaradi delovanja strele, ki lahko povzročijo okvaro elektronskega sistema. Informacije, navedene v dodatku A, pa se lahko kljub temu uporabijo za vrednotenje takih motenj. Ta osnutek mednarodnega standarda ne obravnava podrobnosti projektiranja samih električnih in elektronskih sistemov.

General Information

• Status: Published
• Publication Date: 24-Feb-2011
• Withdrawal Date: 12-Jan-2014
• ICS: 29.020 - Electrical engineering in general
• ICS: 91.120.40 - Lightning protection
• Technical Committee: CLC/TC 81X - Lightning protection
• Drafting Committee: IEC/TC 81 - IEC_TC_81
• Parallel Committee: IEC/TC 81 - IEC_TC_81
• Current Stage: 6060 - Document made available - Publishing
• Start Date: 25-Feb-2011
• Completion Date: 25-Feb-2011
• Ref Project: SIST EN 62305-4:2011 - Protection against lightning - Part 4: Electrical and electronic systems within structures

Relations

• Replaces: EN 62305-4:2006 - Protection against lightning - Part 4: Electrical and electronic systems within structures
• Effective Date: 29-Jan-2023
• Replaced By: EN IEC 62305-4:2024 - Protection against lightning - Part 4: Electrical and electronic systems within structures
• Effective Date: 07-Jun-2022
• Corrected By: EN 62305-4:2011/AC:2016-11 - Protection against lightning - Part 4: Electrical and electronic systems within structures
• Effective Date: 08-Nov-2016

Overview

EN 62305-4:2011 (IEC 62305-4:2010) - "Protection against lightning - Part 4: Electrical and electronic systems within structures" - gives guidance for the design, installation, inspection, maintenance and testing of protection measures for electrical and electronic systems against lightning electromagnetic impulse (LEMP) inside buildings. It is the second edition, a technical revision of the 2006 version, and focuses on reducing permanent failures to internal systems caused by LEMP.

Key topics and technical requirements

• Scope and objective
  • Guidance on Lightning Protection Measures (SPM) for electrical and electronic systems in structures to mitigate LEMP-related damage and malfunctions.
• Lightning Protection Zones (LPZ)
  • Definition and application of LPZs to limit electromagnetic stress on internal systems and to plan progressive protection.
• Surge Protective Devices (SPD)
  • Improved SPD selection guidance considering voltage protection level, downstream oscillation and induction effects; new informative Annex D helps SPD selection.
  • Annex C on SPD coordination withdrawn and referred to SC 37A.
• Isolating interfaces
  • Introduction of isolating interfaces to reduce conducted surges on lines entering a structure.
• Earthing and bonding
  • Requirements for earth-termination systems, bonding networks and equipotential bonding to reduce potential differences and induced currents.
  • Minimum cross-sections for bonding components slightly modified (see normative tables in standard).
• Electromagnetic sources and calculation
  • Use of first negative impulse current as an electromagnetic source of harm for calculation purposes.
• Magnetic shielding and line routing
  • Measures for spatial shielding, cable routing and shielding of internal/external lines to reduce induction.
• SPM management
  • Requirements for inspection, maintenance, testing and an SPM management plan for new and existing structures.

Applications and who uses it

• Practical uses
  • Specification and selection of SPDs and isolating interfaces, design of earthing/bonding networks, LPZ planning, retrofitting existing buildings, and preparing SPM inspection/maintenance schedules.
• Users
  • Electrical and EMC engineers, lightning protection designers, installers, facility managers, asset owners, maintenance teams, and risk managers responsible for critical infrastructure (data centers, telecom sites, industrial plants, hospitals, commercial buildings).

Related standards

• EN/IEC 62305 Series (Parts 1–3) - general principles, risk management, physical damage/life hazard
• IEC 61643 series - low-voltage SPDs (selection, tests, performance)
• IEC 61000 series - EMC testing (surge, magnetic field immunity)

Keywords: EN 62305-4:2011, IEC 62305-4, lightning protection, LEMP, SPDs, surge protection devices, earthing, bonding, LPZ, isolating interfaces, magnetic shielding, SPM management.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2011
1DGRPHãþD
SIST EN 62305-4:2006
=DãþLWDSUHGGHORYDQMHPVWUHOHGHO(OHNWULþQLLQHOHNWURQVNLVLVWHPLY]JUDGEDK
,(&VSUHPHQMHQ
Protection against lightning - Part 4: Electrical and electronic systems within structures
Blitzschutz - Teil 4: Elektrische und elektronische Systeme in baulichen Anlagen
Protection contre la foudre - Partie 4: Réseaux de puissance et de communication dans
les structures
Ta slovenski standard je istoveten z: EN 62305-4:2011
ICS:
91.120.40 =DãþLWDSUHGVWUHOR Lightning protection
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 62305-4
NORME EUROPÉENNE
February 2011
EUROPÄISCHE NORM
ICS 29.020; 91.120.40 Supersedes EN 62305-4:2006 + corr. Nov.2006

English version
Protection against lightning -
Part 4: Electrical and electronic systems within structures
(IEC 62305-4:2010, modified)
Protection contre la foudre -  Blitzschutz - Teil 4: Elektrische und
Partie 4: Réseaux de puissance et de elektronische Systeme in baulichen
communication dans les structures Anlagen
(CEI 62305-4:2010, modifiée) (IEC 62305-4:2010, modifiziert)

This European Standard was approved by CENELEC on 2011-01-13. CENELEC members are bound to comply
with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard
the status of a national standard without any alteration.

Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.

This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and notified
to the Central Secretariat has the same status as the official versions.

CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus,
the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 2011 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62305-4:2011 E
Foreword
The text of document 81/373/FDIS, future edition 2 of IEC 62305-4, prepared by IEC TC 81, Lightning
protection, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 62305-4 on 2011-01-13.
This European Standard supersedes EN 62305-4:2006 + corr. Nov.2006.
This EN 62305-4:2011 includes the following significant technical changes with respect to
EN 62305-4:2006 + corr. Nov.2006:
1) Isolating interfaces capable of reducing conducted surges on lines entering the structure are
introduced.
2) Minimum cross-sections for bonding components are slightly modified.
3) First negative impulse current is introduced for calculation purposes as electromagnetic source of
harm to the internal systems.
4) Selection of SPD with regard to voltage protection level is improved to take into account oscillation
and induction phenomena in the circuit downstream of SPD.
5) Annex C dealing with SPD coordination is withdrawn and referred back to SC 37A.
6) A new informative Annex D is introduced giving information on factors to be considered in the
selection of SPDs.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent
rights.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2011-10-13
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2014-01-13
Annex ZA has been added by CENELEC.
__________
Endorsement notice
The text of the International Standard IEC 62305-4:2010 was approved by CENELEC as a European
Standard without any modification.
In the official version, for Bibliography, the following notes have to be added for the standards indicated:
[2] IEC 61000 series NOTE  Harmonized in EN 61000 series (partially modified).
[8] IEC 61643-11 NOTE  Harmonized as EN 61643-11.
__________
- 3 - EN 62305-4:2011
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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.

NOTE  When an international publication has been modified by common modifications, indicated by (mod), the relevant EN/HD
applies.
Publication Year Title EN/HD Year

IEC 60364-5-53 2001 Electrical installations of buildings - - -
Part 5-53: Selection and erection of electrical
equipment - Isolation, switching and control

IEC 60664-1 2007 Insulation coordination for equipment within EN 60664-1 2007
low-voltage systems -
Part 1: Principles, requirements and tests

IEC 61000-4-5 2005 Electromagnetic compatibility (EMC) - EN 61000-4-5 2006
Part 4-5: Testing and measurement
techniques - Surge immunity test

IEC 61000-4-9 1993 Electromagnetic compatibility (EMC) - EN 61000-4-9 1993
Part 4-9: Testing and measurement
techniques - Pulse magnetic field immunity
test
IEC 61000-4-10 1993 Electromagnetic compatibility (EMC) - EN 61000-4-10 1993
Part 4-10: Testing and measurement
techniques - Damped oscillatory magnetic
field immunity test
IEC 61643-1 2005 Low-voltage surge protective devices - - -
Part 1: Surge protective devices connected to
low-voltage power distribution systems -
Requirements and tests
IEC 61643-12 (mod) 2008 Low-voltage surge protective devices - CLC/TS 61643-12 2009
Part 12: Surge protective devices connected
to low-voltage power distribution systems -
Selection and application principles

IEC 61643-21 - Low voltage surge protective devices - EN 61643-21 -
Part 21: Surge protective devices connected
to telecommunications and signalling
networks - Performance requirements and
testing methods
IEC 61643-22 (mod) - Low-voltage surge protective devices - CLC/TS 61643-22 -
Part 22: Surge protective devices connected
to telecommunications and signalling
networks - Selection and application principles

IEC 62305-1 2010 Protection against lightning - EN 62305-1 2011
Part 1: General principles
IEC 62305-2 2010 Protection against lightning - EN 62305-2 2011
Part 2: Risk management
Publication Year Title EN/HD Year

IEC 62305-3 2010 Protection against lightning - EN 62305-3 2011
Part 3: Physical damage to structures and life
hazard
IEC 62305-4 ®
Edition 2.0 2010-12
INTERNATIONAL
STANDARD
Protection against lightning –
Part 4: Electrical and electronic systems within structures

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
XC
ICS 29.020; 91.120.40 ISBN 978-2-88912-283-7
– 2 – 62305-4 Ó IEC:2010(E)
CONTENTS
FOREW ORD . 5
INTRODUCTION . 7
1 Sc o pe . 9
2 Normative references . 9
3 Terms and definitions . 10
4 Design and installation of SPM. 13
4.1 General . 13
4.2 Design of SPM . 16
4.3 Lightning protection zones (LPZ) . 17
4.4 Basic SPM . 20
5 Earthing and bonding . 21
5.1 General . 21
5.2 Earth-termination system . 22
5.3 Bonding network . 24
5.4 Bonding bars . 28
5.5 Bonding at the boundary of an LPZ . 29
5.6 Material and dimensions of bonding components . 29
6 Magnetic shielding and line routing . 30
6.1 Spatial shielding . 30
6.2 Shielding of internal lines . 30
6.3 Routing of internal lines . 30
6.4 Shielding of external lines . 31
6.5 Material and dimensions of magnetic shields . 31
7 Coordinated SPD system . 31
8 Isolating interfaces . 32
9 SPM management . 32
9.1 General . 32
9.2 SPM management plan . 32
9.3 Inspection of SPM . 33
9.3.1 Inspection procedure . 34
9.3.2 Inspection documentation . 34
9.4 Maintenance . 35
Annex A (informative) Basis of electromagnetic environment evaluation in an LPZ . 36
Annex B (informative) Implementation of SPM for an existing structure . 60
Annex C (informative) Selection and installation of a coordinated SPD system . 76
Annex D (informative) Factors to be considered in the selection of SPDs . 82
Bibliography . 87

Figure 1 – General principle for the division into different LPZ . 13
Figure 2 – Examples of possible SPM (LEMP protection measures) . 15
Figure 3 – Examples for interconnected LPZ . 19
Figure 4 – Examples for extended lightning protection zones . 20
Figure 5 – Example of a three-dimensional earthing system consisting of the bonding
network interconnected with the earth-termination system . 22
Figure 6 – Meshed earth-termination system of a plant . 23

62305-4 Ó IEC:2010(E) – 3 –
Figure 7 – Utilization of reinforcing rods of a structure for equipotential bonding . 25
Figure 8 – Equipotential bonding in a structure with steel reinforcement . 26
Figure 9 – Integration of conductive parts of internal systems into the bonding network . 27
Figure 10 – Combinations of integration methods of conductive parts of internal
systems into the bonding network . 28
Figure A.1 – LEMP situation due to lightning strike . 37
Figure A.2 – Simulation of the rise of magnetic field by damped oscillations . 40
Figure A.3 – Large volume shield built by metal reinforcement and metal frames . 41
Figure A.4 – Volume for electrical and electronic systems inside an inner LPZ n . 42
Figure A.5 – Reducing induction effects by line routing and shielding measures . 43
Figure A.6 – Example of SPM for an office building . 45
Figure A.7 – Evaluation of the magnetic field values in case of a direct lightning strike . 46
Figure A.8 – Evaluation of the magnetic field values in case of a nearby lightning strike . 48
Figure A.9 – Distance s depending on rolling sphere radius and structure dimensions . 50
a
Figure A.10 – Types of grid-like large volume shields . 52
Figure A.11 – Magnetic field strength H inside a grid-like shield type 1 . 53
1/MAX
Figure A.12 – Magnetic field strength H inside a grid-like shield type 1 according
1/MAX
to mesh width. 53
Figure A.13 – Low-level test to evaluate the magnetic field inside a shielded structure . 55
Figure A.14 – Voltages and currents induced into a loop formed by lines . 56
Figure B.1 – SPM design steps for an existing structure . 63
Figure B.2 – Possibilities to establish LPZs in existing structures . 67
Figure B.3 – Reduction of loop area using shielded cables close to a metal plate . 69
Figure B.4 – Example of a metal plate for additional shielding . 70
Figure B.5 – Protection of aerials and other external equipment . 71
Figure B.6 – Inherent shielding provided by bonded ladders and pipes . 72
Figure B.7 – Ideal positions for lines on a mast (cross-section of steel lattice mast) . 72
Figure B.8 – Upgrading of the SPM in existing structures. 74
Figure C.1 – Surge voltage between live conductor and bonding bar . 79
Figure D.1 – Installation example of test Class I, Class II and Class III SPDs . 83
Figure D.2 – Basic example for different sources of damage to a structure and lightning
current distribution within a system. 84
Figure D.3 – Basic example of balanced current distribution . 85

Table 1 – Minimum cross-sections for bonding components . 30
Table 2 – SPM management plan for new buildings and for extensive changes in
construction or use of buildings . 33
Table A.1 – Parameters relevant to source of harm and equipment . 38
Table A.2 – Examples for I = 100 kA and w = 2 m . 48
0/MAX m
Table A.3 – Magnetic attenuation of grid-like spatial shields for a plane wave . 49
Table A.4 – Rolling sphere radius corresponding to maximum lightning current . 51
Table A.5 – Examples for I = 100 kA and w = 2 m corresponding to SF = 12,6 dB . 51
0/MAX m
Table B.1 – Structural characteristics and surroundings . 60
Table B.2 – Installation characteristics . 61
Table B.3 – Equipment characteristics . 61

– 4 – 62305-4 Ó IEC:2010(E)
Table B.4 – Other questions to be considered for the protection concept . 61
Table D.1 – Preferred values of I . 82
imp
62305-4 Ó IEC:2010(E) – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROTECTION AGAINST LIGHTNING –

Part 4: Electrical and electronic systems within structures

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 addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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.
International Standard IEC 62305-4 has been prepared by IEC technical committee 81:
Lightning protection.
This second edition cancels and replaces the first edition, published in 2006, and constitutes
a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
1) Isolating interfaces capable of reducing conducted surges on lines entering the structure
are introduced.
2) Minimum cross-sections for bonding components are slightly modified.
3) First negative impulse current is introduced for calculation purposes as electromagnetic
source of harm to the internal systems.
4) Selection of SPD with regard to voltage protection level is improved to take into account
oscillation and induction phenomena in the circuit downstream of SPD.
5) Annex C dealing with SPD coordination is withdrawn and referred back to SC 37A.

– 6 – 62305-4 Ó IEC:2010(E)
6) A new informative Annex D is introduced giving information on factors to be considered in
the selection of SPDs.
The text of this standard is based on the following documents:
FDIS Report on voting
81/373/FDIS 81/383/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted, as closely as possible, in accordance with the ISO/IEC
Directives, Part 2.
A list of all the parts in the IEC 62305 series, under the general title Protection against
lightning, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
 reconfirmed,
 withdrawn,
 replaced by a revised edition, or
 amended.
A bilingual version of this standard may be issued at a later date.

62305-4 Ó IEC:2010(E) – 7 –
INTRODUCTION
Lightning as a source of harm is a very high energy phenomenon. Lightning flashes release
many hundreds of mega-joules of energy. When compared with the milli-joules of energy that
may be sufficient to cause damage to sensitive electronic equipment in electrical and
electronic systems within a structure, it is clear that additional protection measures will be
necessary to protect some of this equipment.
The need for this International Standard has arisen due to the increasing cost of failures of
electrical and electronic systems, caused by electromagnetic effects of lightning. Of particular
importance are electronic systems used in data processing and storage as well as process
control and safety for plants of considerable capital cost, size and complexity (for which plant
outages are very undesirable for cost and safety reasons).
Lightning can cause different types of damage in a structure, as defined in IEC 62305-1:
D1 injury to living beings by electric shock;
D2 physical damage (fire, explosion, mechanical destruction, chemical release) due to
lightning current effects, including sparking;
D3 failure of internal systems due to LEMP.
IEC 62305-3 deals with the protection measures to reduce the risk of physical damage and
life hazard, but does not cover the protection of electrical and electronic systems.
This Part 4 of IEC 62305 therefore provides information on protection measures to reduce the
risk of permanent failures of electrical and electronic systems within structures.
Permanent failure of electrical and electronic systems can be caused by the lightning
electromagnetic impulse (LEMP) via:
a) conducted and induced surges transmitted to equipment via connecting wiring;
b) the effects of radiated electromagnetic fields directly into equipment itself.
Surges to the structure can originate from sources external to the structure or from within the
structure itself:
– surges which originate externally from the structure are created by lightning flashes
striking incoming lines or the nearby ground, and are transmitted to electrical and
electronic systems within the structure via these lines;
– surges which originate internally within the structure are created by lightning flashes
striking the structure itself or the nearby ground.
NOTE 1 Surges can also originate internally within the structure, from switching effects, e.g. switching of
inductive loads.
The coupling can arise from different mechanisms:
– resistive coupling (e.g. the earth impedance of the earth-termination system or the cable
shield resistance);
– magnetic field coupling (e.g. caused by wiring loops in the electrical and electronic system
or by inductance of bonding conductors);
– electric field coupling (e.g. caused by rod antenna reception).
NOTE 2 The effects of electric field coupling are generally very small when compared to the magnetic field
coupling and can be disregarded.

– 8 – 62305-4 Ó IEC:2010(E)
Radiated electromagnetic fields can be generated via
– the direct lightning current flowing in the lightning channel,
– the partial lightning current flowing in conductors (e.g. in the down-conductors of an
external LPS in accordance with IEC 62305-3 or in an external spatial shield in
accordance with this standard).

62305-4 Ó IEC:2010(E) – 9 –
PROTECTION AGAINST LIGHTNING –

Part 4: Electrical and electronic systems within structures

1 Scope
This part of IEC 62305 provides information for the design, installation, inspection,
maintenance and testing of electrical and electronic system protection (SPM) to reduce the
risk of permanent failures due to lightning electromagnetic impulse (LEMP) within a structure.
This standard does not cover protection against electromagnetic interference due to lightning,
which may cause malfunctioning of internal systems. However, the information reported in
Annex A can also be used to evaluate such disturbances. Protection measures against
[1]
electromagnetic interference are covered in IEC 60364-4-44 and in the IEC 61000 series
[2]
.
This standard provides guidelines for cooperation between the designer of the electrical and
electronic system, and the designer of the protection measures, in an attempt to achieve
optimum protection effectiveness.
This standard does not deal with detailed design of the electrical and electronic systems
themselves.
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 60364-5-53:2001, Electrical installations of buildings – Part 5-53: Selection and erection
of electrical equipment – Isolation, switching and control
IEC 60664-1:2007, Insulation coordination for equipment within low-voltage systems – Part 1:
Principles, requirements and tests
IEC 61000-4-5:2005, Electromagnetic compatibility (EMC) – Part 4-5: Testing and measure-
ment techniques – Surge immunity test
IEC 61000-4-9:1993, Electromagnetic compatibility (EMC) – Part 4-9: Testing and measure-
ment techniques – Pulse magnetic field immunity test – Basic EMC Publication
IEC 61000-4-10:1993, Electromagnetic compatibility (EMC) – Part 4-10: Testing and measure-
ment techniques – Damped oscillatory magnetic field immunity test – Basic EMC Publication
IEC 61643-1:2005, Low-voltage surge protective devices – Part 1: Surge protective devices
connected to low-voltage power distribution systems – Requirements and tests
IEC 61643-12:2008, Low-voltage surge protective devices – Part 12: Surge protective devices
connected to low-voltage power distribution systems – Selection and application principles
___________
Figures in square brackets refer to the bibliography.

– 10 – 62305-4 Ó IEC:2010(E)
IEC 61643-21, Low voltage surge protective devices – Part 21: Surge protective devices
connected to telecommunications and signalling networks – Performance requirements and
testing methods
IEC 61643-22, Low voltage surge protective devices – Part 22: Surge protective devices
connected to telecommunications and signalling networks – Selection and application
principles
IEC 62305-1:2010, Protection against lightning – Part 1: General principles

IEC 62305-2:2010, Protection against lightning – Part 2: Risk management
IEC 62305-3:2010, Protection against lightning – Part 3: Physical damage to structures and
life hazard
3 Terms and definitions
For the purposes of this document, the following terms and definitions, as well as those given
in other parts of IEC 62305, apply.
3.1
electrical system
system incorporating low voltage power supply components
3.2
electronic system
system incorporating sensitive electronic components such as telecommunication equipment,
computer, control and instrumentation systems, radio systems, power electronic installations
3.3
internal systems
electrical and electronic systems within a structure
3.4
lightning protection
LP
complete system for the protection of structures and/or electrical and electronic systems in
those structures from the effects of lightning, consisting of an LPS and SPM
3.5
lightning protection system
LPS
complete system used to reduce physical damage due to lightning flashes to a structure
NOTE It consists of both external and internal lightning protection systems.
3.6
lightning electromagnetic impulse
LEMP
all electromagnetic effects of lightning current via resistive, inductive and capacitive coupling
which create surges and electromagnetic fields
3.7
surge
transient created by LEMP that appears as an overvoltage and/or overcurrent

62305-4 Ó IEC:2010(E) – 11 –
3.8
rated impulse withstand voltage level
U
W
impulse withstand voltage assigned by the manufacturer to the equipment or to a part of it,
characterizing the specified withstand capability of its insulation against overvoltages
NOTE For the purposes of this part of IEC 62305, only withstand voltage between live conductors and earth is
considered.
3.9
lightning protection level
LPL
number related to a set of lightning current parameters relevant to the probability that the
associated maximum and minimum design values will not be exceeded in naturally occurring
lightning
NOTE Lightning protection level is used to design protection measures according to the relevant set of lightning
current parameters.
3.10
lightning protection zone
LPZ
zone where the lightning electromagnetic environment is defined
NOTE The zone boundaries of an LPZ are not necessarily physical boundaries (e.g. walls, floor and ceiling).
3.11
LEMP protection measures
SPM
measures taken to protect internal systems against the effects of LEMP
NOTE This is part of overall lightning protection.
3.12
grid-like spatial shield
magnetic shield characterized by openings
NOTE For a building or a room, it is preferably built by interconnected natural metal components of the structure
(e.g. rods of reinforcement in concrete, metal frames and metal supports).
3.13
earth-termination system
part of an external LPS which is intended to conduct and disperse lightning current into the
earth
3.14
bonding network
interconnecting network of all conductive parts of the structure and of internal systems (live
conductors excluded) to the earth-termination system
3.15
earthing system
complete system combining the earth-termination system and the bonding network
3.16
surge protective device
SPD
device intended to limit transient overvoltages and divert surge currents; contains at least one
non-linear component
– 12 – 62305-4 Ó IEC:2010(E)
3.17
SPD tested with I
imp
SPDs which withstand the partial lightning current with a typical waveform 10/350 ms and
require a corresponding impulse test current I
imp
NOTE For power lines, a suitable test current I is defined in the Class I test procedure of IEC 61643-1:2005.
imp
3.18
SPD tested with I
n
SPDs which withstand induced surge currents with a typical waveform 8/20 ms and require a
corresponding impulse test current I
n
NOTE For power lines a suitable test current I is defined in the Class II test procedure of IEC 61643-1:2005.

n
3.19
SPD tested with a combination wave
SPDs that withstand induced surge currents with a typical waveform 8/20 ms and require a
corresponding impulse test current I
SC
NOTE For power lines a suitable combination wave test is defined in the Class III test procedure of IEC 61643-1:2005
defining the open circuit voltage U 1,2/50 ms and the short-circuit current I 8/20 ms of a 2 W combination wave

OC SC
generator.
3.20
voltage-switching type SPD
SPD that has a high impedance when no surge is present, but can have a sudden change in
impedance to a low value in response to a voltage surge
NOTE 1 Common examples of components used as voltage switching devices include spark gaps, gas discharge
tubes (GDT), thyristors (silicon controlled rectifiers) and triacs. These SPDs are sometimes called "crowbar type“.
NOTE 2 A voltage-switching device has a discontinuous voltage/current characteristic.
3.21
voltage-limiting type SPD
SPD that has a high impedance when no surge is present, but will reduce it continuously with
increased surge current and voltage
NOTE 1 Common examples of components used as non-linear devices are varistors and suppressor diodes.
These SPDs are sometimes called "clamping type“.
NOTE 2 A voltage-limiting device has a continuous voltage/current characteristic.
3.22
combination type SPD
SPD that incorporates both voltage-switching and voltage-limiting type components and that
may exhibit voltage-switching, voltage-limiting or both voltage-switching and voltage-limiting
behaviour, depending upon the characteristics of the applied voltage
3.23
coordinated SPD system
SPDs properly selected, coordinated and installed to form a system intended to reduce
failures of electrical and electronic systems
3.24
isolating interfaces
devices which are capable of reducing conducted surges on lines entering the LPZ
NOTE 1 These include isolation transformers with earthed screen between windings, metal-free fibre optic
cables and opto-isolators.
NOTE 2 Insulation withstand characteristics of these devices are suitable for this application intrinsically or via
SPD.
62305-4 Ó IEC:2010(E) – 13 –
4 Design and installation of SPM
4.1 General
Electrical and electronic systems are subject to damage from a lightning electromagnetic
impulse (LEMP). Therefore SPM need to be provided to avoid failure of internal systems.
The design of SPM should be carried out by experts in lightning and surge protection who
possess a broad knowledge of EMC and installation practices.
Protection against LEMP is based on the lightning protection zone (LPZ) concept: the zone
containing systems to be protected shall be divided into LPZs. These zones are theoretically
assigned part of space (or of an internal system) where the LEMP severity is compatible with
the withstand level of the internal systems enclosed (see Figure 1). Successive zones are
characterized by significant changes in the LEMP severity. The boundary of an LPZ is defined
by the protection measures employed (see Figure 2).

LPZ 0
Antenna
Mast or railing
Electrical
power line
Boundary
of LPZ 2
Boundary
LPZ 1
LPZ 2 of LPZ 1
Equipment
Water
Bonding
pipe Telecommunication
location
line
Bonding of incoming services directly or by suitable SPD
IEC  2762/10
NOTE This figure shows an example of dividing a structure into inner LPZs. All metal services entering the
structure are bonded via bonding bars at the boundary of LPZ 1. In addition, the conductive services entering
LPZ 2 (e.g. computer room) are bonded via bonding bars at the boundary of LPZ 2.
Figure 1 – General principle for the division into different LPZ

– 14 – 62305-4 Ó IEC:2010(E)
I , H
0 0
LPZ 0
LPS + Shield LPZ 1
H
LPZ 1
Shield LPZ 2
H
LPZ 2
H
SPD SPD
(SB) (MB)
Equipment
(object of potential
damage)
U , I U , I U , I
2 2 1 1 0 0
Housing
Partial lightning
current
IEC  2763/10
Figure 2a – SPM using spatial shields and a coordinated SPD system – Equipment well protected
against conducted surges (U < 2 0 2 0 2 0
LPS + Shield LPZ 1
I , H
0 0
LPZ 0
H
LPZ 1
H
SPD
(MB)
Equipment
(object of potential
damage)
U , I
1 1
U , I
0 0
Housing
Partial lightning
current
IEC  2764/10
Figure 2b – SPM using spatial shield of LPZ 1 and SPD protection at entry of LPZ 1 – Equipment protected
against conducted surges (U 1 0 1 0 1 0
62305-4 Ó IEC:2010(E) – 15 –
I , H
0 0
LPZ 0
LPS (No shielding)
LPZ 1
H
H
SPD
Equipment (MB)
H
LPZ 2 2
(object of potential
damage)
U2, I2
U , I
0 0
Partial lightning
Shielded housing
current
or chassis etc.
IEC  2765/10
Figure 2c – SPM using internal line shielding and SPD protection at entry of LPZ 1 – Equipment protected
against conducted surges (U 2 0 2 0 2 0
I , H
0 0
LPS (no shielding)
LPZ 0
H
LPZ 1
H
LPZ 2
SPD
SPD
SPD
Equipment
(SA)
(SB) (MB)
(object of potential
damage)
U , I U , I U , I
2 2 1 1 0 0
Partial lightning
Housing
current
IEC  2766/10
Figure 2d – SPM using a coordinated SPD system only –Equipment protected against conducted
surges (U < 2 0 2 0 0
Key
shielded boundary
non-shielded boundary
NOTE 1 SPDs can be located at the following points:
– at the boundary of LPZ 1 (e.g. at main distribution board MB);
– at the boundary of LPZ 2 (e.g. at secondary distribution board SB);
– at or close to equipment (e.g. at socket outlet SA).
NOTE 2 For detailed installation rules see also IEC 60364-5-53.
Figure 2 – Examples of possible SPM (LEMP protection measures)
Permanent failure of electrical and electronic systems due to LEMP can be caused by
· conducted and induced surges transmitted to equipment via connecting wiring,
· effects of radiated electromagnetic fields impinging directly onto equipment itself.

– 16 – 62305-4 Ó IEC:2010(E)
For protection against the effects of radiated electromagnetic fields impinging directly onto the
equipment, SPM consisting of spatial shields and/or shielded lines, combined with shielded
equipment enclosures, should be used.
For protection against the effects of conducted and induced surges being transmitted to the
equipment via connection wiring, SPM consisting of a coordinated SPD system should be
used.
Failures due to electromagnetic fields impinging directly onto the equipment can be
considered negligible provided the equipment complies with the relevant radio frequency
emission and immunity EMC product standards.
In general, equipment is required to comply with the relevant EMC product standards
therefore SPM consisting of a coordinated SPD system is usually considered sufficient to
protect such equipment against the effects of LEMP.
For equipment not complying with relevant EMC product standards, SPM consisting of a
coordinated SPD system alone is considered inadequate to protect such equipment against
the effects of LEMP. In this case, Annex A provides further information as to how to achieve
best protection against directly impinging electromagnetic fields. The equipment’s withstand
level against radiated magnetic fields needs to be selected in accordance with IEC 61000-4-9
and IEC 61000-4-10.
If required for specific applications, a simulated system-level test which includes the SPD(s),
installation wiring and the actual equipment may be performed in the laboratory to verify
protection withstand coordination.
4.2 Design of SPM
SPM can be designed for protection of equipment against surges and electromagnetic fields.
Figure 2 provides some examples of SPM using protection measures, such as LPS, magnetic
shields and coordinated SPD systems:
· SPM employing spatial shields and a coordinated SPD system will protect against radiated
magnetic fields and against conducted surges (see Figure 2a). Cascaded spatial shields
and coordinated SPDs can reduce the magnetic field and surges to a lower threat level.
· SPM employing a spatial shield of LPZ 1 and an SPD at the entry of LPZ 1 can protect
equipment against the radiated magnetic field and against conducted surges (see
Figure 2b).
NOTE 1 The protection would not be sufficient if the magnetic field remains too high (due to low shielding
effectiveness of LPZ 1), or if the surge magnitude remains too high (due to a high voltage protection level of the
SPD and due to the induction effects onto wiring downstream of the SPD).
· SPM using shielded lines, combined with shielded equipment enclosures, will protect
against radiated magnetic fields. The SPD at the entry of LPZ 1 will provide protection
against conducted surges (see Figure 2c). To achieve a lower threat level (in one step
from LPZ 0 to LPZ 2), a special SPD may be required (e.g. additional coordinated stages
inside) to reach a sufficient low voltage protection level.
· SPM using a coordinated SPD system is only suitable to protect equipment which is
insensitive to radiated magnetic fields, since the SPDs will only provide protection against
conducted surges (see Figure 2d). A lower threat surge level can be achieved using
coordinated SPDs.
NOTE 2 Solutions in accordance with Figures 2a to 2c are recommended especially for equipment which does not
comply with relevant EMC product standards.
NOTE 3 An LPS in accordance with IEC 62305-3 that employs only equipotential bonding SPDs provides no
effective p
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