EN 62305-3:2006

SLOVENSKI STANDARD
01-junij-2006
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SIST IEC 61024-1:1996
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Protection against lightning -- Part 3: Physical damage to structures and life hazard
Blitzschutz -- Teil 3: Schutz von baulichen Anlagen und Personen
Protection contre la foudre -- Partie 3: Dommages physiques sur les structures et risques
humains
Ta slovenski standard je istoveten z: EN 62305-3:2006
ICS:
91.120.40 =DãþLWDSUHGVWUHOR Lightning protection
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 62305-3
NORME EUROPÉENNE
February 2006
EUROPÄISCHE NORM
ICS 29.020; 91.120.40
English version
Protection against lightning
Part 3: Physical damage to structures and life hazard
(IEC 62305-3:2006, modified)
Protection contre la foudre Blitzschutz
Partie 3: Dommages physiques Teil 3: Schutz von baulichen Anlagen
sur les structures et risques humains und Personen
(CEI 62305-3:2006, modifiée) (IEC 62305-3:2006, modifiziert)

This European Standard was approved by CENELEC on 2006-02-01. 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, Cyprus, the Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Rumania, 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

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62305-3:2006 E
Foreword
The text of document 81/264/FDIS, future edition 1 of IEC 62305-3, prepared by IEC TC 81, Lightning
protection, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as
EN 62305-2 on 2006-02-01.
A draft amendment, prepared by the Technical Committee CENELEC TC 81X, Lightning protection,
containing some common modifications to document 81/264/FDIS, was submitted to the formal vote and
was approved by CENELEC on 2006-02-01 for inclusion into EN 62305-2.
The following dates were fixed:
– latest date by which the EN has to be implemented
at national level by publication of an identical
(dop) 2006-11-01
national standard or by endorsement
– latest date by which the national standards conflicting
(dow) 2009-02-01
with the EN have to be withdrawn
This European Standard makes reference to International Standards. Where the International Standard
referred to has been endorsed as a European Standard or a home-grown European Standard exists, this
European Standard shall be applied instead. Pertinent information can be found on the CENELEC web
site.
__________
- 3 - EN 62305-3:2006
Endorsement notice
The text of the International Standard IEC 62305-2:2006 was approved by CENELEC as a European
Standard with agreed common modifications as given below.
COMMON MODIFICATIONS
3 Terms and definitions
Modify the following definitions as follows:
3.16
connecting component
part of an external LPS which is used for the connection of conductors to each other or to metallic
installations, defined as in EN 50164 series
3.17
fixing component
part of an external LPS which is used to fix the elements of the LPS to the structure to be protected,
defined as in EN 50164 series
Annex E
E.4.3.3 Welding or clamping to the steel-reinforcing rods
Modify the Note as follows:
NOTE Specifically designed clamps complying with and tested according to the EN 50164 series shall be used.
E.4.3.7 Down-conductors
Modify the 12th paragraph as follows:
If steel structures are used as down-conductors every steel column shall be connected to the steel
reinforcing rods of the concrete foundation according to Figure E.8 by proprietary bonding points
complying with the EN 50164 series
E.5.2.4.1 General information
Modify the first paragraph as follows:
The maximum permissible temperature for a conductor will not be exceeded if the cross-section complies
with Table 6 and the EN 50164 series.
E.5.2.4.2 Non-isolated air-termination
Add at the end of the second paragraph:
NOTE Z1  For more details see EN 50164 series.
E.5.5 Components
Replace the text of the subclause by:
Components of LPS shall withstand the electromagnetic effects of lightning current and predictable
accidental stresses without being damaged. This can be achieved by choosing components that have
successfully been tested in accordance with the EN 50164 series.
All components shall comply with the EN 50164 series.

E.5.6.1 Mechanical design
Modify the 6th paragraph as follows:
The LPS designer and the LPS installer should specify conductor fasteners and fixtures which will
withstand the electrodynamic forces of lightning current in the conductors and also allow for the
expansion and contraction of conductors due to the relevant temperature rise according to the EN 50164
series.
E.5.6.2.1 Materials
Modify the first paragraph 1 as follows:
LPS materials and conditions of use are listed in Table 5 and the EN 50164 series.
E.5.6.2.2.1 Metals in soil and air
Modify the Note as follows:
NOTE Spark gaps having a protection level U of 2,5 kV and a minimum I of 50 kA (10/350 µs) complying with EN 50164-3 are
p imp
suitable.
IEC 62305-3
Edition 1.0 2006-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Protection against lightning –
Part 3: Physical damage to structures and life hazard

Protection contre la foudre –
Partie 3: Dommages physiques sur les structures et risques humains

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XG
CODE PRIX
ICS 29.020; 91.120.40 ISBN 2-8318-8366-0

62305-3 © IEC:2006 – 3 – – 2 – 62305-3 © IEC:2006
CONTENTS
FOREWORD. 6
INTRODUCTION. 8

1 Scope. 9
2 Normative references . 9
3 Terms and definitions .10
4 Lightning protection system (LPS) .13
4.1 Class of LPS .13
4.2 Design of the LPS .14
4.3 Continuity of steelwork in reinforced concrete structures .14
5 External lightning protection system .15
5.1 General .15
5.2 Air-termination systems.15
5.3 Down-conductor systems.19
5.4 Earth-termination system.22
5.5 Components .24
5.6 Materials and dimensions .26
6 Internal lightning protection system .29
6.1 General .29
6.2 Lightning equipotential bonding .29
6.3 Electrical insulation of the external LPS .32
7 Maintenance and inspection of an LPS .33
7.1 Application of inspections.33
7.2 Order of inspections .33
7.3 Maintenance.33
8 Protection measures against injury to living beings due to touch and step voltages .34
8.1 Protection measures against touch voltages.34
8.2 Protection measures against step voltages.34

Annex A (normative) Positioning the air-termination system.35
Annex B (normative) Minimum cross-section of the entering cable screen in order to
avoid dangerous sparking .41
Annex C (informative) Partitioning of the lightning current amongst down-conductors .42
Annex D (informative) Additional information for LPS in the case of structures with a
risk of explosion.46
Annex E (informative) Guidelines for the design, construction, maintenance and
inspection of lightning protection systems . 52

Bibliography.154

62305-3 © IEC:200662305-3 © IEC:2006 – 5 – – 3 –
Figure 1 – Loop in a down-conductor .20
Figure 2 – Minimum length l of each earth electrode according to the class of LPS.22
Figure A.1 – Volume protected by a vertical air-termination rod .35
Figure A.2 – Volume protected by a vertical air-termination rod .36
Figure A.3 – Volume protected by a wire air-termination system .36
Figure A.4 – Volume protected by isolated wires combined in a mesh according to the
protective angle method and rolling sphere method .37
Figure A.5 – Volume protected by non-isolated wires combined in a mesh according to
the mesh method and the protective angle method .38
Figure A.6 – Design of an air-termination system according to the rolling sphere
method .39
Figure C.1 – Values of coefficient k in the case of a wire air-termination system and a
c
type B earth-termination system.43
Figure C.2 – Values of coefficient k in the case of a mesh air-termination system and
c
type B earth-termination system.44
Figure C.3 – Examples of calculation of the separation distance in the case of a
meshed air-termination system, an interconnecting ring of the down-conductors at
each level and a type B earth-termination system .45
Figure E.1 – LPS design flow diagram . 54
Figure E.2 – Values of coefficient k in case of a sloped roof with air-termination on
c
the ridge and a type B earthing system . 61
Figure E.3 – LPS design for a cantilevered part of a structure. 62
Figure E.4 – Equipotential bonding in a structure with a steel reinforcement . 64
Figure E.5 – Welded joints of reinforcing rods in reinforced concrete, if permitted. 65
Figure E.6 – Example of clamps used as joints between reinforcing rods and
conductors. 66
Figure E.7 – Examples for connection points to the reinforcement in a reinforced
concrete wall . 67
Figure E.8 – Use of metallic facade as natural down-conductor system and connection
of facade supports . 70
Figure E.9 – Connection of the continuous strip windows to a metal façade covering. 72
Figure E.10 – Internal down-conductors in industrial structures. 75
Figure E.11– Installation of bonding conductors in reinforced concrete structures and
flexible bonds between two reinforced concrete parts . 77
Figure E.12 – Protective angle method air-termination design for different heights
according to Table 2 . 81
Figure E.13 – Isolated external LPS using two isolated air-termination masts designed
according to the protective angle air-termination design method . 82
Figure E.14 – Isolated external LPS using two isolated air-termination masts,
interconnected by horizontal catenary wire . 83
Figure E.15 – Example of design of an air-termination of a non-isolated LPS by air-
termination rods. 84
Figure E.16 – Example of design of an air-termination of a non isolated LPS by a
horizontal wire according to the protective angle air-termination design method . 85
Figure E.17 – Protected volume of an air- termination rod or mast on a sloped surface. 86

62305-3 © IEC:2006 – 7 – – 4 – 62305-3 © IEC:2006
Figure E.18 – Design of an LPS air-termination according to the rolling sphere method,
protective angle method, mesh method and general arrangement of air-termination
elements. 88
Figure E.19 – Design of an LPS air-termination conductor network on a structure with
complicated shape. 89
Figure E.20 – Space protected by two parallel air-termination horizontal wires or two
air-termination rods (r > h ). 90
t
Figure E.21 – Points at which lightning will strike a building. 92
Figure E.22 – Example of design of non-isolated LPS air-termination according to the
mesh method air-termination design . 96
Figure E.23 – Some examples of details of an LPS on a structure with sloped tiled roofs. 99
Figure E.24 – Construction of an LPS using natural components on the roof of the
structure .101
Figure E.25 – Positioning of the external LPS on a structure made of insulating
material e.g. wood or bricks with a height up to 60 m with flat roof and with roof fixtures .102
Figure E.26 – Construction of air-termination network on a roof with conductive
covering where puncturing of the covering is not acceptable.103
Figure E.27 – Construction of external LPS on a structure of steel-reinforced concrete
using the reinforcement of the outer walls as natural components.104
Figure E.28 – Example of an air-termination stud used on car park roofs .105
Figure E.29 – Air-termination rod used for protection of a metallic roof fixture with
electric power installations which are not bonded to the air-termination system .106
Figure E.30 – Method of achieving electrical continuity on metallic parapet cladding .107
Figure E.31 – Metallic roof fixture protected against direct lightning interception,
connected to air-termination system.110
Figure E.32 – Example of construction of lightning protection of a house with a TV
antenna using the mast as an air-termination rod.112
Figure E.33 – Installation of lightning protection of metallic equipment on a roof against
a direct lightning flash.113
Figure E.34 – Connection of natural air-termination rod to air-termination conductor.115
Figure E.35 – Construction of the bridging between the segments of the metallic
façade plates .116
Figure E.36 – Installation of external LPS on a structure of isolating material with
different roof levels .118
Figure E.37 – Examples of geometry of LPS conductors .119
Figure E.38 – Construction of an LPS using only two down-conductors and foundation
earth electrodes.120
Figure E.39 – Examples of connection of earth termination to the LPS of structures
using natural down-conductors (girders) and detail of a test joint .124
Figure E.40 – Construction of foundation earth ring for structures of different
foundation design .128
Figure E.41 – Examples of two vertical electrodes in type A earthing arrangement .130
Figure E.42 – Meshed earth termination system of a plant .134

62305-3 © IEC:200662305-3 © IEC:2006 – 9 – – 5 –
Figure E.43 – Examples of separation distance between the LPS and metal
installations .140
Figure E.44 – Directions for calculations of the separation distance s for a worst case
lightning interception point at a distance l from the reference point according to 6.3 .141
Figure E.45 – Example of an equipotential bonding arrangement .144
Figure E.46 – Example of bonding arrangement in a structure with multiple point
entries of external conductive parts using a ring electrode for interconnection of
bonding bars.145
Figure E.47 – Example of bonding in the case of multiple point entries of external
conductive parts and an electric power or communication line using an internal ring
conductor for interconnection of the bonding bars .146
Figure E.48 – Example of bonding arrangement in a structure with multiple point
entries of external conductive parts entering the structure above ground level .147

Table 1 – Relation between lightning protection levels (LPL) and class of LPS (see
IEC 62305-1) .13
Table 2 – Maximum values of rolling sphere radius, mesh size and protection angle
corresponding to the class of LPS.16
Table 3 – Minimum thickness of metal sheets or metal pipes in air-termination systems .18
Table 4 – Typical values of the distance between down-conductors and between ring
conductors according to the class of LPS.20
Table 5 – LPS materials and conditions of use.25
Table 6 – Material, configuration and minimum cross-sectional area of air-termination
conductors, air-termination rods and down-conductors.27
Table 7 – Material, configuration and minimum dimensions of earth electrodes.28
Table 8 – Minimum dimensions of conductors connecting different bonding bars or
connecting bonding bars to the earth-termination system.30
Table 9 – Minimum dimensions of conductors connecting internal metal installations to
the bonding bar.30
Table 10 – Isolation of external LPS – Values of coefficient k .32
i
Table 11 – Isolation of external LPS – Values of coefficient k .32
c
Table 12 – Isolation of external LPS – Values of coefficient k .33
m
Table B.1 – Cable length to be considered according to the condition of the screen.41
Table C.1 – Values of coefficient k .42
c
Table E.1 – Suggested fixing centres. 97
Table E.2 – Maximum period between inspections of an LPS.149

62305-3 © IEC:2006 –– 6 – 11 – 62305-3 © IEC:2006
INTERNATIONAL ELECTROTECHNICAL COMMISSION
___________
PROTECTION AGAINST LIGHTNING –

Part 3: Physical damage to structures and life hazard

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC national committees). The object of the IEC is to promote
international cooperation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, the 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. The 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 the 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, the 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) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to the 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. The IEC shall not be held responsible for identifying any or all such patent rights.
International standard IEC 62305-3 has been prepared by IEC technical committee 81:
Lightning protection.
The IEC 62305 series (Parts 1 to 5), is produced in accordance with the new Publications`
Plan, approved by National Committees (81/171/RQ (2001-06-29)), which restructures in a
more simple and rational form and updates the Publications of the IEC 61024 series, the IEC
61312 series and the IEC 61663 series.
The text of this first edition of IEC 62305-3 is compiled from and replaces
– IEC 61024-1, first edition (1990).
– IEC 61024-1-2, first edition (1998).

62305-3 © IEC:200662305-3 © IEC:2006 –– 7 – 13 –
The text of this standard is based on the following documents:
FDIS Report on voting
81/264/FDIS 81/269/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 close as possible, in accordance with the ISO/IEC
Directives, Part 2.
IEC 62305 consists of the following parts, under the general title Protection against lightning:
Part 1: General principles
Part 2: Risk management
Part 3: Physical damage to structures and life hazard
Part 4: Electrical and electronic systems within structures
Part 5: Services
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC website "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.
In the United States, based on the requirements of NFPA 780: Standard for the Installation of Lightning Protection
Systems 2004 Edition and practical experience in the use of horizontal earth electrodes, the minimum length of
horizontal earth electrodes is not required to be twice that required for vertical electrodes.
In France, Portugal and Spain:
– natural components cannot substitute as lightning protection components but may be used to
complete/enhance the LPS;
– aluminium solid round diameters should be extended from 8 mm to 10 mm;
– stranded conductors cannot be used as down-conductors;
– diameter of solid round conductors should be extended from 16 mm to 18 mm;
– hot dip galvanized steel solid tape thickness should be extended from 2 mm to 3,5 mm.

———————
To be published
62305-3 © IEC:2006 –– 8 – 15 – 62305-3 © IEC:2006
INTRODUCTION
This part of IEC 62305 deals with the protection, in and around a structure, against physical
damage and injury to living beings due to touch and step voltages.
The main and most effective measure for protection of structures against physical damage is
considered to be the lightning protection system (LPS). It usually consists of both external
and internal lightning protection systems.
An external LPS is intended to:
a) intercept a lightning flash to the structure (with an air-termination system);
b) conduct the lightning current safely towards earth (using a down-conductor system);
c) disperse the lightning current into the earth (using an earth-termination system).
An internal LPS prevents dangerous sparking within the structure using either equipotential
bonding or a separation distance (and hence electrical insulation) between the external LPS
(as defined in 3.2) components and other electrically conducting elements internal to the
structure.
Main protection measures against injury to living beings due to touch and step voltages are
intended to:
1) reduce the dangerous current flowing through bodies by insulating exposed conductive
parts, and/or by increasing the surface soil resistivity;
2) reduce the occurrence of dangerous touch and step voltages by physical restrictions
and/or warning notices.
The type and location of an LPS should be carefully considered in the initial design of a new
structure, thereby enabling maximum advantage to be taken of the electrically conductive
parts of the structure. By doing so, design and construction of an integrated installation is
made easier, the overall aesthetic aspects can be improved, and the effectiveness of the LPS
can be increased at minimum cost and effort.
Access to the ground and the proper use of foundation steelwork for the purpose of forming
an effective earth termination may well be impossible once construction work on a site has
commenced. Therefore, soil resistivity and the nature of the earth should be considered at the
earliest possible stage of a project. This information is fundamental to the design of an earth-
termination system and may influence the foundation design work for the structure.
Regular consultation between LPS designers and installers, architects and builders is
essential in order to achieve the best result at minimum cost.
If lightning protection is to be added to an existing structure, every effort should be made to
ensure that it conforms to the principles of this standard. The design of the type and location
of an LPS should take into account the features of the existing structure.

62305-3 © IEC:200662305-3 © IEC:2006 –– 9 – 17 –
PROTECTION AGAINST LIGHTNING –

Part 3: Physical damage to structures and life hazard

1 Scope
This part of IEC 62305 provides the requirements for protection of a structure against physical
damage by means of a lightning protection system (LPS), and for protection against injury to
living beings due to touch and step voltages in the vicinity of an LPS (see IEC 62305-1).
This standard is applicable to:
a) design, installation, inspection and maintenance of an LPS for structures without limitation
of their height;
b) establishment of measures for protection against injury to living beings due to touch and
step voltages.
NOTE 1 Specific requirements for an LPS in structures dangerous to their surroundings due to the risk of explosion are
under consideration. Additional information is provided in Annex D for use in the interim.
NOTE 2 This part of IEC 62305 is not intended to provide protection against failures of electrical and electronic
systems due to overvoltages. Specific requirements for such cases are provided in IEC 62305-4.
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 60079-10:2002, Electrical apparatus for explosive gas atmospheres – Part 10:
Classification of hazardous areas
IEC 60079-14:2002, Electrical apparatus for explosive gas atmospheres – Part 14: Electrical
installations in hazardous areas (other than mines)
IEC 61241-10:2004, Electrical apparatus for use in the presence of combustible dust –
Part 10: Classification of areas where combustible dusts are or may be present
IEC 61241-14:2004, Electrical apparatus for use in the presence of combustible dust –
Part 14: Selection and installation
IEC 61643-12:2002, Low-voltage surge protective devices – Part 12: Surge protective devices
connected to low voltage power distribution systems – Selection and application principles
IEC 62305-1, Protection against lightning – Part 1: General principles
IEC 62305-2, Protection against lightning – Part 2: Risk management
IEC 62305-4, Protection against lightning – Part 4: Electrical and electronic systems within
structures
62305-3 © IEC:2006 –– 10 – 19 – 62305-3 © IEC:2006
IEC 62305-5, Protection against lightning – Part 5: Services
ISO 3864-1, Graphical symbols – Safety colours and safety signs – Part 1: Design principles
for safety signs in workplaces and public areas
3 Terms and definitions
For the purposes of this document, the following terms and definitions, some of which have
already been cited in Part 1 but are repeated here for ease of reference, as well as those
given in other parts of IEC 62305, apply.
3.1
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.
3.2
external lightning protection system
part of the LPS consisting of an air-termination system, a down-conductor system and an
earth-termination system
3.3
external LPS isolated from the structure to be protected
LPS with an air-termination system and down-conductor system positioned in such a way that
the path of the lightning current has no contact with the structure to be protected
NOTE In an isolated LPS, dangerous sparks between the LPS and the structure are avoided.
3.4
external LPS not isolated from the structure to be protected
LPS with an air-termination system and down-conductor system positioned in such a way that
the path of the lightning current can be in contact with the structure to be protected
3.5
internal lightning protection system
part of the LPS consisting of lightning equipotential bonding and/or electrical insulation of
external LPS
3.6
air-termination system
part of an external LPS using metallic elements such as rods, mesh conductors or catenary
wires intended to intercept lightning flashes
3.7
down-conductor system
part of an external LPS intended to conduct lightning current from the air-termination system
to the earth-termination system
———————
To be published
62305-3 © IEC:200662305-3 © IEC:2006 –– 11 – 21 –
3.8
ring conductor
conductor forming a loop around the structure and interconnecting the down-conductors for
distribution of lightning current among them
3.9
earth-termination system
part of an external LPS which is intended to conduct and disperse lightning current into the
earth
3.10
earthing electrode
part or a group of parts of the earth-termination system which provides direct electrical
contact with the earth and disperses the lightning current into the earth
3.11
ring earthing electrode
earthing electrode forming a closed loop around the structure below or on the surface of the
earth
3.12
foundation earthing electrode
reinforcing steel of foundation or additional conductor embedded in the concrete foundation of
a structure and used as an earthing electrode
3.13
conventional earth impedance
ratio of the peak values of the earth-termination voltage and the earth-termination current
which, in general, do not occur simultaneously
3.14
earth-termination voltage
potential difference between the earth-termination system and the remote earth
3.15
natural component of LPS
conductive component installed not specifically for lightning protection which can be used in
addition to the LPS or in some cases could provide the function of one or more parts of the
LPS
NOTE Examples of the use of this term include:
– natural air-termination;
– natural down-conductor;
– natural earthing electrode.
3.16
connecting component
part of an external LPS which is used for the connection of conductors to each other or to
metallic installations
3.17
fixing component
part of an external LPS which is used to fix the elements of the LPS to the structure to be
protected
62305-3 © IEC:2006 –– 12 – 23 – 62305-3 © IEC:2006
3.18
metal installations
extended metal items in the structure to be protected which may form a path for lightning
current, such as pipework, staircases, elevator guide rails, ventilation, heating and air-
conditioning ducts, and interconnected reinforcing steel
3.19
external conductive parts
extended metal items entering or leaving the structure to be protected such as pipework,
metallic cable elements, metal ducts, etc. which may carry a part of the lightning current
3.20
electrical system
system incorporating low voltage power supply components and possibly electronic
components
3.21
electronic system
system incorporating sensitive electronic components such as communication equipment,
computer, control and instrumentation systems, radio systems, power electronic installations
3.22
internal systems
electrical and electronic systems within a structure
3.23
lightning equipotential bonding
EB
bonding to the LPS of separated conductive parts, by direct connections or via surge
protective devices, to reduce potential differences caused by lightning current
3.24
bonding bar
metal bar on which metal installations, external conductive parts, electric power and tele-
communication lines, and other cables can be bonded to an LPS
3.25
bonding conductor
conductor connecting separated conductive parts to LPS
3.26
interconnected reinforcing steel
steelwork within a concrete structure which is considered electrically continuous
3.27
dangerous sparking
electrical discharge due to lightning which causes physical damage in the structure to be
protected
3.28
separation distance
distance between two conductive parts at which no dangerous sparking can occur

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3.29
surge protective device
SPD
device that is intended to limit transient overvoltages and divert surge currents. It contains at
least one non-linear component
3.30
test joint
joint designed to facilitate electrical testing and measurement of LPS components
3.31
class of LPS
number denoting the classification of an LPS according to the lightning protection level for
which it is designed
3.32
lightning protection designer
specialist competent and skilled in the design of the LPS
3.33
lightning protection installer
person competent and skilled in the installation of the LPS
3.34
structures with risk of explosion
structures containing solid explosives materials or hazardous zones as determined in
accordance with IEC 60079-10 and IEC 61241-10
4 Lightning protection system (LPS)
4.1 Class of LPS
The characteristics of an LPS are determined by the characteristics of the structure to be
protected and by the considered lightning protection level.
Four classes of LPS (I to IV) are defined in this standard corresponding to lightning protection
levels defined in IEC 62305-1 (see Table 1).
Table 1 – Relation between lightning protection levels (LPL)
and class of LPS (see IEC 62305-1)
LPL Class of LPS
I I
II II
III III
IV IV
Each class of LPS is characterized by the following.
a) Data dependent upon the class of LPS:
– lightning parameters (see Tables 3 and 4 in IEC 62305-1);
– rolling sphere radius, mesh size and protection angle (see 5.2.2);
– typical distances between down-conductors and between ring conductors (see 5.3.3);
– separation distance against dangerous sparking (see 6.3);
– minimum length of earth electrodes (see 5.4.2).

62305-3 © IEC:2006 –– 14 – 27 – 62305-3 © IEC:2006
b) Data not dependent upon the class of LPS:
– lightning equipotential bonding (see 6.2);
– minimum thickness of metal sheets or metal pipes in air-termination systems (see
5.2.5);
– LPS materials and conditions of use (see 5.5);
– material, configuration and minimum dimensions for air-terminations, down-conductors
and earth-terminations (see 5.6);
– minimum dimensions of connecting conductors (see 6.2.2).
Performance of each class of LPS is given in Annex B of IEC 62305-2.
The class of required LPS shall be selected on the basis of a risk assessment (see IEC 62305-2).
4.2 Design of the LPS
A technically and economically optimized design of an LPS is possible especially if the steps
in the design and construction of the LPS are coordinated with the steps in the design and
construction of the structure to be protected. In particular, the design of the structure itself
should utilize the metal parts of the structure as parts of the LPS.
The design of the class and location of the LPS for existing structures shall take into account
the constraints of the existing
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