EN IEC 62305-2:2024
(Main)Protection against lightning - Part 2: Risk management
Protection against lightning - Part 2: Risk management
IEC 62305-2:2024 is applicable to the risk management of a structure due to lightning flashes to earth. Its purpose is to provide a procedure for the evaluation of such a risk. Once an upper tolerable limit for the risk has been selected, this procedure provides a means for the selection of appropriate protection measures to be adopted to reduce the risk to or below the tolerable limit. This third edition cancels and replaces the second edition, published in 2010. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a) The concept of a single risk, to combine loss of human life and loss due to fire, has been introduced. b) The concept of frequency of damage that can impair the availability of the internal systems within the structure has been introduced. c) The lightning ground strike-point density NSG has been introduced replacing the lightning flash density NG in the evaluation of expected average annual number of dangerous events. d) Reduction of a few risk components can be achieved by the use of preventive temporary measures activated by means of a thunderstorm warning system (TWS) compliant with IEC 62793. The risk of direct strike to people in open areas has been introduced, considering the reduction of that risk using a TWS.
Blitzschutz - Teil 2: Risiko-Management
Protection contre la foudre - Partie 2: Évaluation des risques
L'IEC 62305-2:2024 s'applique à l'évaluation des risques auxquels une structure est exposée en raison des coups de foudre à la terre. Elle est destinée à proposer une procédure d'évaluation d'un tel risque. Lorsque la limite supérieure du risque tolérable est fixée, la procédure permet de choisir les mesures de protection appropriées pour réduire le risque à une valeur inférieure ou égale à la valeur limite tolérable. Cette troisième édition annule et remplace la deuxième édition parue en 2010. Cette édition constitue une révision technique. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente: a) adoption du concept de risque unique, afin de combiner les pertes de vies humaines et les pertes dues à un incendie; b) adoption du concept de fréquence des dommages qui peuvent influencer la disponibilité des réseaux internes à la structure; c) adoption de la densité de points d'impact au sol de la foudre NSG en remplacement de la densité des coups de foudre NG dans l'évaluation du nombre moyen annuel d'événements dangereux prévisibles; d) la réduction de quelques composantes de risque peut être obtenue par l'utilisation de mesures préventives temporaires activées par un système d'alerte aux orages (TWS) conforme à l'IEC 62793. Le risque que des personnes soient directement frappées par la foudre dans des espaces ouverts a été décrit, en tenant compte de la réduction de ce risque au moyen d'un TWS.
Zaščita pred delovanjem strele - 2. del: Obvladovanje tveganja
Standard IEC 62305-2:2024 se uporablja za obvladovanje tveganja za zgradbo zaradi udara strele v zemljo.
Njegov namen je določiti postopek za ocenjevanje takšnega tveganja. Ko je izbrana zgornja sprejemljiva meja za tveganje, ta postopek omogoča izbor ustreznih zaščitnih ukrepov za zmanjšanje tveganja na sprejemljivo mejo ali pod njo.
Tretja izdaja razveljavlja in nadomešča drugo izdajo, objavljeno leta 2010. Ta izdaja je tehnično popravljena izdaja.
Ta izdaja v primerjavi s prejšnjo vključuje naslednje pomembne tehnične spremembe:
a) Uveden je bil koncept posameznega tveganja, ki združuje izgubo človeškega življenja in izgubo zaradi požara.
b) Uveden je koncept pogostosti poškodb, ki lahko vplivajo na razpoložljivost notranjih sistemov znotraj zgradbe.
c) Uvedena je bila gostota točk udarov strele proti zemlji (NSG), ki je pri ocenjevanju pričakovanega povprečnega letnega števila nevarnih dogodkov nadomestila gostoto strel proti zemlji (NG).
d) Zmanjšanje nekaterih komponent tveganja je mogoče doseči s preventivnimi začasnimi ukrepi, ki jih aktivira sistem za opozarjanje pred nevihtami (TWS), skladen s standardom IEC 62793. Tveganje neposrednega udara v ljudi na odprtih območjih je bilo uvedeno ob upoštevanju, da se takšno tveganje zmanjša s sistemom za opozarjanje pred nevihtami.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-december-2024
Nadomešča:
SIST EN 62305-2:2012
Zaščita pred delovanjem strele - 2. del: Obvladovanje tveganja
Protection against lightning - Part 2: Risk management
Blitzschutz - Teil 2: Risiko-Management
Protection contre la foudre - Partie 2: Evaluation des risques
Ta slovenski standard je istoveten z: EN IEC 62305-2:2024
ICS:
91.120.40 Zaščita pred strelo Lightning protection
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EUROPEAN STANDARD EN IEC 62305-2
NORME EUROPÉENNE
EUROPÄISCHE NORM October 2024
ICS 29.020; 91.120.40 Supersedes EN 62305-2:2012
English Version
Protection against lightning - Part 2: Risk management
(IEC 62305-2:2024)
Protection contre la foudre - Partie 2: Évaluation des Blitzschutz - Teil 2: Risiko-Management
risques (IEC 62305-2:2024)
(IEC 62305-2:2024)
This European Standard was approved by CENELEC on 2024-10-17. 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 CEN-CENELEC
Management Centre 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 CEN-CENELEC Management Centre 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, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Türkiye and the United Kingdom.
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members.
Ref. No. EN IEC 62305-2:2024 E
European foreword
The text of document 81/769/FDIS, future edition 3 of IEC 62305-2, prepared by TC 81 "Lightning
protection" was submitted to the IEC-CENELEC parallel vote and approved by CENELEC as
The following dates are fixed:
• latest date by which the document has to be implemented at national (dop) 2025-10-31
level by publication of an identical national standard or by endorsement
• latest date by which the national standards conflicting with the (dow) 2027-10-31
document have to be withdrawn
This document supersedes EN 62305-2:2012 and all of its amendments and corrigenda (if any).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CENELEC shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national committee. A
complete listing of these bodies can be found on the CENELEC website.
Endorsement notice
The text of the International Standard IEC 62305-2:2024 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 standard indicated:
IEC 60364-4-44 NOTE Approved as HD 60364-4-444
IEC 61000-4-5:2014 NOTE Approved as EN 61000-4-5:2014 (not modified)
IEC 60079-10-1 NOTE Approved as EN IEC 60079-10-1
IEC 60079-10-2 NOTE Approved as EN 60079-10-2
IEC 60664-1:2020 NOTE Approved as EN IEC 60664-1:2020 (not modified)
IEC 61643-11:2011 NOTE Approved as EN 61643-11:2012 +A11:2018
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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 1 Where an International Publication has been modified by common modifications, indicated by (mod),
the relevant EN/HD applies.
NOTE 2 Up-to-date information on the latest versions of the European Standards listed in this annex is available
here: www.cencenelec.eu.
Publication Year Title EN/HD Year
IEC 61643 series Low-voltage surge protective devices -- EN IEC 61643 series
Part 1: Surge protective devices connected
to low-voltage power distribution systems -
Requirements and tests
IEC 62305-1 2024 Protection against lightning - Part 1: EN IEC 62305-1 2024
General principles
IEC 62305-3 2024 Protection against lightning - Part 3: EN IEC 62305-3 2024
Physical damage to structures and life
hazard
IEC 62305-4 2024 Protection against lightning - Part 4: EN IEC 62305-4 2024
Electrical and electronic systems within
structures
IEC 62793 - Thunderstorm warning systems - EN IEC 62793 -
Protection against lightning
IEC 62858 - Lightning density based on lightning EN IEC 62858 -
location systems (LLS) - General principles
IEC 62305-2 ®
Edition 3.0 2024-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Protection against lightning –
Part 2: Risk management
Protection contre la foudre –
Partie 2: Évaluation des risques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 29.020, 91.120.40 ISBN 978-2-8322-9549-6
– 2 – IEC 62305-2:2024 © IEC 2024
CONTENTS
FOREWORD . 8
INTRODUCTION . 11
1 Scope . 13
2 Normative references . 13
3 Terms and definitions . 13
4 Symbols and abbreviated terms . 21
5 Damage and loss . 25
5.1 Source of damage . 25
5.2 Cause of damage . 25
5.3 Type of loss . 25
6 Risk and risk components . 26
6.1 Risk . 26
6.2 Risk components . 27
6.2.1 Risk components for a structure due to source S1 . 27
6.2.2 Risk component for a structure due to source S2 . 28
6.2.3 Risk components for a structure due to source S3 . 28
6.2.4 Risk component for a structure due to source S4 . 28
6.2.5 Factors affecting risk components for a structure . 28
6.3 Composition of risk components . 29
6.3.1 Composition of risk components according to source of damage . 29
6.3.2 Composition of risk components according to type of loss . 30
7 Risk assessment . 31
7.1 Basic procedure . 31
7.2 Structure to be considered for risk assessment . 31
7.3 Procedure to evaluate the need of protection for risk R . 31
8 Assessment of risk components . 33
8.1 Basic equation . 33
8.2 Assessment of risk components due to different sources of damage . 34
8.3 Partitioning of a structure in risk zones Z . 36
S
8.4 Partitioning of a line into sections S . 37
L
8.5 Assessment of risk components in a zone of a structure with risk zones Z . 38
S
8.5.1 General criteria . 38
8.5.2 Single-zoned structure . 38
8.5.3 Multi-zoned structure . 38
9 Frequency of damage and its components . 39
9.1 Frequency of damage . 39
9.2 Assessment of partial frequency of damage . 39
9.3 Procedure to evaluate the need of protection for frequency of damage F . 40
9.4 Assessment of partial frequency of damage in zones . 42
9.4.1 General criteria . 42
9.4.2 Single-zoned structure . 42
9.4.3 Multi-zoned structure . 42
Annex A (informative) Assessment of annual number N of dangerous events . 43
A.1 General . 43
IEC 62305-2:2024 © IEC 2024 – 3 –
A.2 Assessment of the average annual number of dangerous events N due to
D
flashes to a structure and N to an adjacent structure . 44
DJ
A.2.1 Determination of the collection area A . 44
D
A.2.2 Structure as a part of a building . 46
A.2.3 Relative location of the structure . 48
A.2.4 Number of dangerous events N for the structure . 48
D
A.2.5 Number of dangerous events N for an adjacent structure . 49
DJ
A.3 Assessment of the average annual number of dangerous events N due to
M
flashes near a structure . 49
A.4 Assessment of the average annual number of dangerous events N due to
L
flashes to a line . 50
A.5 Assessment of average annual number of dangerous events N due to
I
flashes near a line . 51
A.6 Representation of the equivalent collection areas . 52
Annex B (informative) Assessment of probability P of damage . 53
X
B.1 General . 53
B.2 Probability P that a flash to a structure will cause dangerous touch and
AT
step voltages . 54
B.3 Probability P that a flash will cause damage to an exposed person on the
AD
structure . 55
B.4 Probability P that a flash to a structure will cause physical damage by fire
B
or explosion . 57
B.5 Probability P that a flash to a structure will cause failure of internal
C
systems . 59
B.6 Probability P that a flash near a structure will cause failure of internal
M
systems . 63
B.7 Probability P that a flash to a line will cause damage due to touch voltage . 65
U
B.8 Probability P that a flash to a line will cause physical damage by fire or
V
explosion . 67
B.9 Probability P that a flash to a line will cause failure of internal systems . 68
W
B.10 Probability P that a lightning flash near an incoming line will cause failure
Z
of internal systems . 69
B.11 Probability P that a person will be in a dangerous place . 69
P
B.12 Probability P that an equipment will be exposed to a damaging event . 70
e
Annex C (informative) Assessment of loss L . 71
X
C.1 General . 71
C.2 Mean relative loss per dangerous event . 71
Annex D (informative) P evaluation . 74
SPD
D.1 General . 74
D.2 P values . 75
Q
D.2.1 Probability values of both the negative and positive first strokes . 75
D.2.2 Source of damage S1 . 75
D.2.3 Source of damage S3 . 76
D.2.4 Sources of damage S2 and S4. 77
D.3 SPD protection level . 77
D.3.1 General . 77
– 4 – IEC 62305-2:2024 © IEC 2024
D.3.2 Source of damage S1 . 77
D.3.3 Source of damage S3 . 81
D.3.4 Energy coordinated SPDs: One voltage switching SPD and one voltage
limiting SPD downstream . 85
D.4 Source of damage S4 . 88
D.4.1 One voltage limiting SPD . 88
D.4.2 One voltage switching SPD . 88
D.5 Source of damage S2 . 89
Annex E (informative) Detailed investigation of additional losses L related to
E
surroundings . 90
E.1 General . 90
E.2 Calculation of risk components . 90
Annex F (informative) Case studies . 94
F.1 General . 94
F.2 House . 94
F.2.1 Relevant data and characteristics . 94
F.2.2 Calculation of expected annual number of dangerous events . 96
F.2.3 Risk management . 97
F.2.4 Definition of risk zones in the house . 97
F.2.5 Risk assessment . 99
F.2.6 Risk – Selection of protection measures . 99
F.2.7 Conclusions . 100
F.3 Office building . 100
F.3.1 Relevant data and characteristics . 100
F.3.2 Calculation of expected annual number of dangerous events . 101
F.3.3 Risk management . 102
F.3.4 Definition of zones in the office building . 103
F.3.5 Risk assessment . 107
F.3.6 Frequency of damage assessment . 108
F.3.7 Risk – Selection of protection measures . 108
F.3.8 Frequency of damage – Selection of protection measures . 109
F.3.9 Conclusions . 110
F.4 Hospital . 110
F.4.1 Relevant data and characteristics . 110
F.4.2 Calculation of expected annual number of dangerous events . 111
F.4.3 Risk management . 112
F.4.4 Definition of zones in the hospital . 112
F.4.5 Risk assessment . 117
F.4.6 Frequency of damage assessment . 118
F.4.7 Risk – Selection of protection measures . 118
F.4.8 Frequency of damage – Selection of protection measures . 120
F.4.9 Conclusions . 120
Bibliography . 121
Figure 1 – Procedure for deciding the need for protection and for the selection of
protection measures to reduce R ≤ R . 33
T
Figure 2 – Example of zone partitioning . 37
Figure 3 – Procedure for determining the need for protection and for the selection of
protection measures . 41
IEC 62305-2:2024 © IEC 2024 – 5 –
Figure A.1 – Collection area A of an isolated structure . 44
D
Figure A.2 – Complex-shaped structure . 45
Figure A.3 – Different methods to determine the collection area for a given structure . 46
Figure A.4 – Structure to be considered for evaluation of collection area A . 47
D
Figure A.5 – Equivalent collection areas A , A , A , A and A . 52
D DJ M L l
Figure D.1 – Charge probability of both negative and positive first strokes . 76
Figure D.2 – Probability P as a function of the SPD residual voltage U ’ at 1 kA . 78
Up p
Figure D.3 – Probability P as a function of k . 79
Up 1i
Figure D.4 – Probability P as a function of the SPD2 residual voltage U ’ at 1 kA . 80
Up p
Figure D.5 – Probability P as a function of the SPD2 residual voltage U ’ at 1 kA . 81
Up p
Figure D.6 – Probability P as a function of the residual voltage at 1 kA (U ’) . 82
Up p
Figure D.7 – Probability P as a function of different lengths of the internal circuit . 83
Up
Figure D.8 – Probability P as a function of different lengths of the internal circuit . 83
Up
Figure D.9 – Probability P as a function of the SPD2 residual voltage U ’ at 1 kA . 85
Up p
Figure D.10 – Probability P as a function of the internal loop area for n' = 2 and
Up
w = 0,1 m . 86
Figure D.11 – Probability P as a function of the internal loop area for n' = 2 and
Up
w = 0,5 m . 87
Figure D.12 – Probability P as a function of the internal loop area for n' = 20 and
Up
w = 0,1 m . 87
Figure D.13 – Probability P as a function of the SPD protection level U ’ at 1 kA for
Up p
different internal loop areas . 88
Figure D.14 – Probability P as a function of different internal loop areas for two
Up
typical protection levels of GDTs . 89
Table 1 – Sources of damage, causes of damage, types of loss and risk components
according to the point of strike . 27
Table 2 – Factors influencing the risk components . 29
Table 3 – Risk components for different sources of damage and types of loss . 35
Table 4 – Partial frequency of damage for each source of damage . 40
Table A.1 – Structure location factors C and C . 48
D DJ
Table A.2 – Line installation factor C . 50
I
Table A.3 – Line type factor C . 51
T
Table A.4 – Environmental factor C . 51
E
Table B.1 – Values of probability P that a flash to a structure will cause damage due
am
to touch and step voltages according to different protection measures . 55
Table B.2 – Reduction factor r as a function of the type of surface of soil or floor . 55
t
Table B.3 – Values of probability P depending on the protection measures to
LPS
protect the exposed areas of the structure against the direct flash and to reduce
physical damage . 56
Table B.4 – Values of probability P that a flash to a structure will cause dangerous
S
sparking . 57
– 6 – IEC 62305-2:2024 © IEC 2024
Table B.5 – Reduction factor r as a function of provisions taken to reduce the
p
consequences of fire . 58
Table B.6 – Reduction factor r as a function of risk of fire or explosion of structure. 58
f
Table B.7 – Typical values of P for SPDs on the low-voltage system, used to
SPD
protect against sources of damage S1, S2, S3, S4 . 60
Table B.8 – Typical values of P for SPDs on the telecommunications system used
SPD
to protect against sources of damage S1, S2, S3, S4 . 61
Table B.9 – Values of factors C and C depending on shielding, grounding and
LD LI
isolation conditions . 62
Table B.10 – Value of factor K depending on internal wiring . 65
S3
Table B.11 – Values of the probability P depending on the resistance R of the
LD S
cable screen and the impulse withstand voltage U of the equipment . 66
W
Table B.12 – Values of the probability P depending on the resistance R of the
LD S
cable screen and the higher impulse withstand voltage U of the equipment . 67
W
Table B.13 – Typical values of probability P relevant to protection level LPL for
EB
which the SPD is designed to protect against source of damage S3 . 67
Table C.1 – Loss values for each zone . 72
Table C.2 – Typical mean values of L , L , L , L , L and L . 73
T D F1 F2 O1 O2
Table D.1 – P values of the voltage limiting SPD for combination between a voltage
Up
limiting and a voltage switching SPD . 79
Table D.2 – P values of the voltage limiting SPD . 84
Up
Table E.1 – Risk components for different sources of damage and types of loss, valid
for damage to the surroundings . 91
Table E.2 – Type of loss L1: Proposed typical values for the related time of presence
for people t /8 760 in different environments as limited by Table E.3 . 92
zE
Table E.3 – Type of loss L1: Typical mean values of L and L outside the
F1E O1E
structure . 93
Table E.4 – Type of loss L2: Typical mean values of L and L outside the
F2E O2E
structure . 93
Table F.1 – House: environment and structure characteristics . 95
Table F.2 – House: power line . 95
Table F.3 – House: telecom line . 96
Table F.4 – House: equivalent collection areas of structure and lines . 96
Table F.5 – House: expected annual number of dangerous events . 97
Table F.6 – House: time of presence of persons and risk components into risk zones . 98
Table F.7 – House: values for zone Z (inside the building) . 98
–5
Table F.8 – House: risk for the unprotected structure (values × 10 ) . 99
–5
Table F.9 – House: risk components for protected structure (values × 10 ). 100
Table F.10 – Office building: environment and structure characteristics . 100
Table F.11 – Office building: power line . 101
Table F.12 – Office building: telecom line . 101
Table F.13 – Office building: collection areas of structure and lines . 102
Table F.14 – Office building: expected annual number of dangerous events . 102
IEC 62305-2:2024 © IEC 2024 – 7 –
Table F.15 – Office building: time of presence of persons and risk components in
zones . 103
Table F.16 – Office building: factors valid for zone Z (entrance area outside) . 104
Table F.17 – Office building: factors valid for zone Z (roof) . 104
Table F.18 – Office building: factors valid for zone Z (archive) . 105
Table F.19 – Office building: factors valid for zone Z (offices) . 106
Table F.20 – Office building: factors valid for zone Z (computer centre) . 107
–5
Table F.21 – Office building: risk for the unprotected structure (values × 10 ) . 108
Table F.22 – Office building: frequency of damage for the unprotected structure . 108
–5
Table F.23 – Risk components for protected structure (values × 10 ) . 109
Table F.24 – Office building: frequency of damage for protected structure . 109
Table F.25 – Hospital: environment and structure characteristics . 110
Table F.26 – Hospital: power line . 111
Table F.27 – Hospital: collection areas of structure and power line . 111
Table F.28 – Hospital: expected annual number of dangerous events . 112
Table F.29 – Hospital: time of presence of persons and risk components in zones . 113
Table F.30 – Hospital: factors valid for zone Z (outside the building) . 113
Table F.31 – Hospital: factors valid for zone Z (roof) . 114
Table F.32 – Hospital: factors valid for zone Z (rooms) . 115
Table F.33 – Hospital: factors valid for zone Z (operating block) . 116
Table F.34 – Hospital: factors valid for zone Z (intensive care unit) . 117
–5
Table F.35 – Hospital: risk for the unprotected structure (values × 10 ) . 118
Table F.36 – Hospital: frequency of damage for the unprotected structure . 118
–5
Table F.37 – Hospital: risk for the protected structure (values × 10 ) . 119
Table F.38 – Hospital: frequency of damage for the protected structure . 120
– 8 – IEC 62305-2:2024 © IEC 2024
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
PROTECTION AGAINST LIGHTNING –
Part 2: Risk management
FOREWORD
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IEC 62305-2 has been prepared by IEC technical committee 81: Lightning protection. It is an
International Standard.
This third edition cancels and replaces the second edition, published in 2010. This edition
constitutes a technical revision.
This edition includes the following significant technical changes with respect to the previous
edition:
a) The concept of a single risk, to combine loss of human life and loss due to fire, has been
introduced.
b) The concept of frequency of damage that can impair the availability of the internal systems
within the structure has been introduced.
IEC 62305-2:2024 © IEC 2024 – 9 –
c) The lightning ground strike-point density N has been introduced replacing the lightning
SG
flash density N in the evaluation of expected average annual number of dangerous events.
G
d) Reduction of a few risk components can be achieved by the use of preventive temporary
measures activated by means of a thunderstorm warning system (TWS) compliant with
IEC 62793. The risk of direct strike to people in open areas has been introduced,
considering the reduction of that risk using a TWS.
The text of this International Standard is based on the following documents:
Draft Report on voting
81/769/FDIS 81/772/RVD
Full information on the voting for its approval can be found in the report on voting indicated in
the above table.
The language used for the development of this International Standard is English.
This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in
accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available
at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are
described in greater detail at www.iec.ch/publications.
A list of all parts in the IEC 62305 series, published under the general title Protection against
lightning, can be found on the IEC website.
The following differing practices of a less permanent nature exist in the countries indicated
below.
In Germany, the value of r = 1 applies for all cases. For the risk components R , R , R , R ,
p B C M V
R and R P = 1 is assumed. For LF1 and LF2 the highest values given in Table C.2 should
W Z TWS
be used.
In Greece, the value of P = 1 for all cases is assumed.
TWS
In Italy, calculating both the risk of loss of human life, RL1 in Equation (7), and the risk of loss
due to physical damages, RL2 in Equation (8), and comparing each risk with the tolerable risk
is required. Protection is achieved when both risks, RL1 and RL2, are less than the tolerable
value.
In the Netherlands and South Africa, Annex D and Annex E should not be applied for usual
studies.
– 10 – IEC 62305-2:2024 © IEC 2024
The committee has decided that the contents of this document will remain unchanged until the
stability date indicated on the IEC website under webstore.iec.ch in the data related to the
specific document. At this date, the document will be
• reconfirmed,
• withdrawn, or
• revised.
IMPORTANT – The "colour inside" logo on the cover page of this document indicates
that it contains colours which are considered to be useful for the correct understanding
of its contents. Users should therefore print this document using a colour printer.
The content of the corrigendum 1 (2024-10) has been included in this copy.
IEC 62305-2:2024 © IEC 2024 – 11 –
INTRODUCTION
Lightning flashes to earth can be hazardous to structures and to lines supplying the structure.
These hazards can result in:
– damage to the structure and to its contents,
– failure of associated electrical and electronic systems,
– injury to living beings in or close to the structure.
Consequential effects of the damage and failures can be extended to the surroundings of the
structure or can involve its environment. Moreover, regardless of the extent of loss, the
availability of the structure and its internal systems can be unacceptably impaired if the
frequency of damage is high.
To reduce the frequency of damage and the loss due to lightning, protection measures can be
required. Whether they are necessary, and to what extent, should be determined by frequency
of damage and risk assessment.
NOTE 1 The decision to provide lightning protection can be taken regardless of the outcome of frequency of damage
or risk assessment where there is a desire that there be no avoidable damages.
NOTE 2 IEC 60364-4-44 [1] always requires the installation of a surge protective device (SPD) at the power line
entrance in the structure when the consequence caused by overvoltages affects:
– care of human life, e.g. safety services, medical care facilities,
– public services and cultural heritage, e.g. loss of public services, IT centres, museums,
– commercial or industrial activity, e.g. hotels, banks, industries, commercial markets, farms.
The frequency of damage, defined in this document as the annual number of damages in a
structure due to lightning flashes, depends on:
– the annual number of lightning flashes influencing the structure;
– the probability of damaging events by one of the influencing lightning flashes.
The risk, defined in this document as the probable average annual loss in a structure due to
lightning flashes, depends on:
– the frequency of damage;
– the mean extent of consequential loss.
Lightning flashes influencing the structure can be divided into
– flashes terminating on the structure,
– flashes terminating near the structure, directly to connected lines (power, telecom-
munication lines) or near the lines.
Flashes to the structure or a connected line can cause physical damage and life hazards.
Flashes near the structure or li
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