EN 62305-2:2012

SLOVENSKI STANDARD
01-julij-2012
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SIST EN 62305-2:2006
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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 62305-2:2012
ICS:
91.120.40 =DãþLWDSUHGVWUHOR Lightning protection
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 62305-2
NORME EUROPÉENNE
May 2012
EUROPÄISCHE NORM
ICS 29.020; 91.120.40 Supersedes EN 62305-2:2006 + corr. Nov.2006

English version
Protection against lightning -
Part 2: Risk management
(IEC 62305-2:2010, modified)
Protection contre la foudre -  Blitzschutz -
Partie 2: Evaluation des risques Teil 2: Risiko-Management
(CEI 62305-2:2010, modifiée) (IEC 62305-2:2010, modifiziert)

This European Standard was approved by CENELEC on 2012-03-19. 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, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland, Turkey 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

© 2012 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 62305-2:2012 E
Contents
For e wor d . 6
Introduction . 7
1 Scope . 8
2 Normative references . 8
3 Terms, definitions, symbols and abbreviations . 8
3.1 Terms and definitions . 8
3.2 Symbols and abbreviations . 13
4 Explanation of terms . 16
4.1 Damage and loss . 16
4.2 Risk and risk components . 18
4.3 Composition of risk components . 20
5 Risk management . 21
5.1 Basic procedure . 21
5.2 Structure to be considered for risk assessment . 22
5.3 Tolerable risk R . 22
T
5.4 Specific procedure to evaluate the need of protection . 22
5.5 Procedure to evaluate the cost effectiveness of protection . 23
5.6 Protection measures . 26
5.7 Selection of protection measures . 26
6 Assessment of risk components . 26
6.1 Basic equation . 26
6.2 Assessment of risk components due to flashes to the structure (S1) . 27
6.3 Assessment of the risk component due to flashes near the structure (S2) . 27
6.4 Assessment of risk components due to flashes to a line connected to the structure
(S3) . 27
6.5 Assessment of risk component due to flashes near a line connected to the
structure (S4) . 28
6.6 Summary of risk components . 29
6.7 Partitioning of a structure in zones Z . 29
S
6.8 Partitioning of a line into sections S . 30
L
6.9 Assessment of risk components in a structure with zones Z . 30
S
6.10 Cost-benefit analysis for economic loss (L4) . 31
Annex A (informative) Assessment of annual number N of dangerous events . 32
A.1 General . 32
A.2 Assessment of the average annual number of dangerous events N due to flashes
D
to a structure and N to an adjacent structure . 32
DJ
A.3 Assessment of the average annual number of dangerous events N due to
M
flashes near a structure . 37
A.4 Assessment of the average annual number of dangerous events N due to flashes
L
to a line. 38
A.5 Assessment of average annual number of dangerous events N due to flashes
I
near a line. 39
Annex B (informative) Assessment of probability P of damage . 40
X
B.1 General . 40
B.2 Probability P that a flash to a structure will cause injury to living beings by
A
electric shock . 40
B.3 Probability P that a flash to a structure will cause physical damage . 41
B
– 3 – EN 62305-2:2012
B.4 Probability P that a flash to a structure will cause failure of internal systems . 41
C
B.5 Probability P that a flash near a structure will cause failure of internal systems . 43
M
B.6 Probability P that a flash to a line will cause injury to living beings by electric
U
shock . 44
B.7 Probability P that a flash to a line will cause physical damage . 45
V
B.8 Probability P that a flash to a line will cause failure of internal systems . 46
W
B.9 Probability P that a lightning flash near an incoming line will cause failure of
Z
internal systems . 46
Annex C (informative) Assessment of amount of loss L . 48
X
C.1 General . 48
C.2 Mean relative amount of loss per dangerous event . 48
C.3 Loss of human life (L1) . 48
C.4 Unacceptable loss of service to the public (L2) . 51
C.5 Loss of irreplaceable cultural heritage (L3) . 52
C.6 Economic loss (L4) . 53
Annex D (informative) Evaluation of costs of loss . 56
Annex E (informative) Case study . 57
E.1 General . 57
E.2 Country house . 57
E.3 Office building . 62
E.4 Hospital . 69
E.5 Apartment block . 80
Bibliography . 85
Figures
Figure 1 – Procedure for deciding the need of protection and for selecting protection
measures . 24
Figure 2 – Procedure for evaluating the cost-effectiveness of protection measures . 25
Figure A.1 – Collection area A of an isolated structure . 33
D
Figure A.2 – Complex shaped structure . 34
Figure A.3 – Different methods to determine the collection area for the given structure . 35
Figure A.4 – Structure to be considered for evaluation of collection area A . 36
D
Figure A.5 – Collection areas (A , A , A , A ) . 39
D M I L
Figure E.1 – Country house . 57
Figure E.2 – Office building . 62
Figure E.3 – Hospital . 69
Figure E.4 – Apartment block . 81
Tables
Table 1 – Sources of damage, types of damage and types of loss according to the point of
strike . 18
Table 2 – Risk components to be considered for each type of loss in a structure . 20
Table 3 – Factors influencing the risk components . 21
Table 4 – Typical values of tolerable risk R . 22
T
Table 5 – Parameters relevant to the assessment of risk components . 28
Table 6 – Risk components for different types of damage and source of damage . 29
Table A.1 – Structure location factor C . 37
D
Table A.2 – Line installation factor C . 38
I
Table A.3 – Line type factor C . 38
T
Table A.4 – Line environmental factor C . 38
E
Table B.1 – Values of probability P that a flash to a structure will cause shock to living
TA
beings due to dangerous touch and step voltages . 40
Table B.2 – Values of probability P depending on the protection measures to reduce
B
physical damage . 41
Table B.3 – Value of the probability P as a function of LPL for which SPDs are designed42
SPD
Table B.4 – Values of factors C and C depending on shielding, grounding and isolation
LD LI
c o n d i t i o n s . 42
Table B.5 – Value of factor K depending on internal wiring . 44
S3
Table B.6 – Values of probability P that a flash to an entering line will cause shock to
TU
living beings due to dangerous touch voltages . 45
Table B.7 – Value of the probability P as a function of LPL for which SPDs are designed 45
EB
Table B.8 – Values of the probability P depending on the resistance R of the cable
LD S
screen and the impulse withstand voltage U of the equipment . 45
W
Table B.9 – Values of the probability P depending on the line type and the impulse
LI
withstand voltage U of the equipment . 47
W
Table C.1 – Type of loss L1: Loss values for each zone . 49
Table C.2 – Type of loss L1: Typical mean values of L , L and L . 49
T F O
Table C.3 – Reduction factor r as a function of the type of surface of soil or floor . 50
t
Table C.4 – Reduction factor r as a function of provisions taken to reduce the
p
consequences of fire . 50
Table C.5 – Reduction factor r as a function of risk of fire or explosion of structure . 51
f
Table C.6 – Factor h increasing the relative amount of loss in presence of a special hazard51
z
Table C.7 – Type of loss L2: Loss values for each zone . 52
Table C.8 – Type of loss L2: Typical mean values of L and L . 52
F O
Table C.9 – Type of loss L3: Loss values for each zone . 52
Table C.10 – Type of loss L3: Typical mean value of L . 53
F
Table C.11 – Type of loss L4: Loss values for each zone . 53
Table C.12 – Type of loss L4: Typical mean values of L , L and L . 54
T F O
Table C.Z1 – Values to assess the total value c . 54
t
Table C.Z2 – Portions to assess the total values c , c , c , c . 55
a b c s
Table E.1 – Country house: Environment and structure characteristics . 58
Table E.2 – Country house: Power line . 58
Table E.3 – Country house: Telecom line (TLC) . 59
Table E.4 – Country house: Factors valid for zone Z (inside the building) . 60
Table E.5 – Country house: Collection areas of structure and lines . 60
Table E.6 – Country house: Expected annual number of dangerous events . 61
–5
Table E.7 – Country house: Risk R for the unprotected structure (values × 10 ) . 61
Table E.8 – Country house: Risk components relevant to risk R for protected structure . 62
Table E.9 – Office building: Environment and structure characteristics . 63
Table E.10 – Office building: Power line . 63
Table E.11 – Office building: Telecom line . 64
Table E.12 – Office building: Distribution of persons into zones . 64
Table E.13 – Office building: Factors valid for zone Z (entrance area outside) . 65
Table E.14 – Office building: Factors valid for zone Z (garden outside) . 65
– 5 – EN 62305-2:2012
Table E.15 – Office building: Factors valid for zone Z (archive) . 66
Table E.16 – Office building: Factors valid for zone Z (offices) . 66
Table E.17 – Office building: Factors valid for zone Z (computer centre) . 67
Table E.18 – Office building: Collection areas of structure and lines . 67
Table E.19 – Office building: Expected annual number of dangerous events . 68
–5
Table E.20 – Office building: Risk R for the unprotected structure (values × 10 ) . 68
–5
Table E.21 – Office building: Risk R for the protected structure (values × 10 ) . 69
Table E.22 – Hospital: Environment and global structure characteristics . 70
Table E.23 – Hospital: Power line . 70
Table E.24 – Hospital: Telecom line . 71
Table E.25 – Hospital: Distribution of persons and of economic values into zones . 72
Table E.26 – Hospital: Factors valid for zone Z (outside the building) . 73
Table E.27 – Hospital: Factors valid for zone Z (rooms block) . 73
Table E.28 – Hospital: Factors valid for zone Z (operating block) . 74
Table E.29 – Hospital: Factors valid for zone Z (intensive care unit) . 75
Table E.30 – Hospital: Collection areas of structure and lines . 75
Table E.31 – Hospital: Expected annual number of dangerous events . 76
Table E.32 – Hospital: Risk R – Values of probability P for the unprotected structure . 76
–5
Table E.33 – Hospital: Risk R for the unprotected structure (values × 10 ) . 77
Table E.34 – Hospital: Risk R for the protected structure according to solution a)
-5
(values × 10 ) . 78
Table E.35 – Hospital: Risk R for the protected structure according to solution b)
-5
(values × 10 ) . 78
Table E.36 – Hospital: Risk R for the protected structure according to solution c)
-5
(values × 10 ) . 79
Table E.37 – Hospital: Cost of loss C (unprotected) and C (protected) . 79
L RL
Table E.38 – Hospital: Rates relevant to the protection measures . 80
Table E.39 – Hospital: Cost C and C of protection measures (values in $) . 80
P PM
Table E.40 – Hospital: Annual saving of money (values in $) . 80
Table E.41 – Apartment block: Environment and global structure characteristics . 81
Table E.42 – Apartment block: Power line . 82
Table E.43 – Apartment block: Telecom line . 82
Table E.44 – Apartment block: Factors valid for zone Z (inside the building). 83
Table E.45 – Apartment block: Risk R for the apartment block depending on protection
measures . 84

Foreword
This document (EN 62305-2:2012) consists of the text of IEC 62305-2:2010 prepared by IEC/TC 81,
"Lightning protection", together with the common modifications prepared by CLC/TC 81X, "Lightning
protection".
The following dates are fixed:
(dop) 2013-03-19
• latest date by which this document has to be
implemented
at national level by publication of an identical
national standard or by endorsement
(dow) 2014-01-13
• latest date by which the national standards conflicting
with this document have to be withdrawn
This document supersedes EN 62305-2:2006 + corrigendum November 2006.
EN 62305-2:2006:
1) risk assessment for services connected to structures is excluded from the scope;
2) injuries of living beings caused by electric shock inside the structure are considered;
-3 -4
3) tolerable risk of loss of cultural heritage is lowered from 10 to 10 ;
4) extended damage to surroundings structures or to the environment is considered;
5) improved formulas are provided for evaluation of
– collection areas relevant to flashes nearby a structure,
– collection areas relevant to flashes to and nearby a line,
– probabilities that a flash can cause damage,
– loss factors even in structures with risk of explosion,
– risk relevant to a zone of a structure,
– cost of loss.
6) tables are provided to select the relative amount of loss in all cases;
7) impulse withstand voltage level of equipments was extended down to 1 kV.
Notes and tables, which are additional to those in IEC 62305-2:2010 are prefixed “Z”.
In this document, the common modifications to IEC 62305-2:2010 are indicated by a vertical line in
the left margin of the text.
Attention is drawn to the possibility that some of the elements of this document may be the subject
of patent rights. CENELEC [and/or CEN] shall not be held responsible for identifying any or all such
patent rights.
– 7 – EN 62305-2:2012
Introduction
Lightning flashes to earth may be hazardous to structures and to lines.
The hazard to a structure 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 may be extended to the surroundings of the
structure or may involve its environment.
To reduce the loss due to lightning, protection measures may be required. Whether they are
needed, and to what extent, should be determined by risk assessment.
The risk, defined in this part of EN 62305 as the probable average annual loss in a structure due to
lightning flashes, depends on
– the annual number of lightning flashes influencing the structure,
– the probability of damage by one of the influencing lightning flashes,
– the mean amount of consequential loss.
Lightning flashes influencing the structure may be divided into
– flashes terminating on the structure,
– flashes terminating near the structure, direct to connected lines (power, telecommunication
lines,) or near the lines.
Flashes to the structure or a connected line may cause physical damage and life hazards. Flashes
near the structure or line as well as flashes to the structure or line may cause failure of electrical
and electronic systems due to overvoltages resulting from resistive and inductive coupling of these
systems with the lightning current.
Moreover, failures caused by lightning overvoltages in users’ installations and in power supply lines
may also generate switching type overvoltages in the installations.
NOTE  Malfunctioning of electrical and electronic systems is not covered by the EN 62305 series. Reference should be
[2] )
made to EN 61000-4-5 .
The number of lightning flashes influencing the structure depends on the dimensions and the
characteristics of the structure and of the connected lines, on the environmental characteristics of
the structure and the lines, as well as on lightning ground flash density in the region where the
structure and the lines are located.
The probability of lightning damage depends on the structure, the connected lines, and the lightning
current characteristics, as well as on the type and efficiency of applied protection measures.
The annual mean amount of the consequential loss depends on the extent of damage and the
consequential effects which may occur as result of a lightning flash.
The effect of protection measures results from the features of each protection measure and may
reduce the damage probabilities or the amount of consequential loss.
The decision to provide lightning protection may be taken regardless of the outcome of risk
assessment where there is a desire that there be no avoidable risk.
___________
1) Figures in square brackets refer to the bibliography.

1 Scope
This part of EN 62305 is applicable to risk assessment for 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 allows the selection of appropriate protection
measures to be adopted to reduce the risk to or below the tolerable limit.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
EN 62305-1:2011, Protection against lightning – Part 1: General principles (IEC 62305-1:2010,
mod.)
EN 62305-3:2011, Protection against lightning – Part 3: Physical damage to structures and life
hazard (IEC 62305-3:2010, mod.)
EN 62305-4:2011, Protection against lightning – Part 4: Electrical and electronic systems within
structures (IEC 62305-4:2010, mod.)
3 Terms, definitions, symbols and abbreviations
For the purposes of this document, the following terms, definitions, symbols and abbreviations,
some of which have already been cited in Part 1 but are repeated here for ease of reading, as well
as those given in other parts of EN 62305, apply.
3.1 Terms and definitions
3.1.1
structure to be protected
structure for which protection is required against the effects of lightning in accordance with this
standard
Note 1 to entry: A structure to be protected may be part of a larger structure.
3.1.2
structures with risk of explosion
structures containing solid explosives materials or hazardous zones as determined in accordance
[3] [4]
with EN 60079-10-1 and EN 60079-10-2
3.1.3
structures dangerous to the environment
structures which may cause biological, chemical or radioactive emission as a consequence of
lightning (such as chemical, petrochemical, nuclear plants, etc.)
3.1.4
urban environment
area with a high density of buildings or densely populated communities with tall buildings
Note 1 to entry: ’Town centre’ is an example of an urban environment.
3.1.5
suburban environment
area with a medium density of buildings

– 9 – EN 62305-2:2012
Note 1 to entry: ‘Town outskirts’ is an example of a suburban environment.
3.1.6
rural environment
area with a low density of buildings
Note 1 to entry: Countryside’ is an example of a rural environment.
3.1.7
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 (transient) overvoltages
[5]
[SOURCE: EN 60664-1:2007, definition 3.9.2, modified]
Note 1 to entry: For the purposes of this part of EN 62305, only the withstand voltage between live conductors and earth is
considered.
3.1.8
electrical system
system incorporating low voltage power supply components
3.1.9
electronic system
system incorporating sensitive electronic components such as telecommunication equipment,
computer, control and instrumentation systems, radio systems, power electronic installations
3.1.10
internal systems
electrical and electronic systems within a structure
3.1.11
line
power line or telecommunication line connected to the structure to be protected
3.1.12
telecommunication lines
lines intended for communication between equipment that may be located in separate structures,
such as phone lines and data lines
3.1.13
power lines
distribution lines feeding electrical energy into a structure to power electrical and electronic
equipment located there, such as low voltage (LV) or high voltage (HV) electric mains
3.1.14
dangerous event
lightning flash to or near the structure to be protected, or to or near a line connected to the structure
to be protected that may cause damage
3.1.15
lightning flash to a structure
lightning flash striking a structure to be protected
3.1.16
lightning flash near a structure
lightning flash striking close enough to a structure to be protected that it may cause dangerous
overvoltages
3.1.17
lightning flash to a line
lightning flash striking a line connected to the structure to be protected
3.1.18
lightning flash near a line
lightning flash striking close enough to a line connected to the structure to be protected that it may
cause dangerous overvoltages
3.1.19
number of dangerous events due to flashes to a structure
N
D
expected average annual number of dangerous events due to lightning flashes to a structure
3.1.20
number of dangerous events due to flashes to a line
N
L
expected average annual number of dangerous events due to lightning flashes to a line
3.1.21
number of dangerous events due to flashes near a structure
N
M
expected average annual number of dangerous events due to lightning flashes near a structure
3.1.22
number of dangerous events due to flashes near a line
N
I
expected average annual number of dangerous events due to lightning flashes near a line
3.1.23
lightning electromagnetic impulse
LEMP
all electromagnetic effects of lightning current via resistive, inductive and capacitive coupling, which
create surges and electromagnetic fields
3.1.24
surge
transient created by LEMP that appears as an overvoltage and/or overcurrent
3.1.25
node
point on a line from which onward surge propagation can be assumed to be neglected
Note 1 to entry: Examples of nodes are a point on a power line branch distribution at an HV/LV transformer or on a power
substation, a telecommunication exchange or an equipment (e.g. multiplexer or xDSL equipment) on a telecommunication
line.
3.1.26
physical damage
damage to a structure (or to its contents) due to mechanical, thermal, chemical or explosive effects
of lightning
3.1.27
injury to living beings
permanent injuries, including loss of life, to people or to animals by electric shock due to touch and
step voltages caused by lightning
Note 1 to entry: Although living beings may be injured in other ways, in this part of EN 62305 the term ‘injury to living
beings’ is limited to the threat due to electrical shock (type of damage D1).

– 11 – EN 62305-2:2012
3.1.28
failure of electrical and electronic systems
permanent damage of electrical and electronic systems due to LEMP
3.1.29
probability of damage
P
X
probability that a dangerous event will cause damage to or in the structure to be protected
3.1.30
loss
L
X
mean amount of loss (humans and goods) consequent on a specified type of damage due to a
dangerous event, relative to the value (humans and goods) of the structure to be protected
3.1.31
risk
R
value of probable average annual loss (humans and goods) due to lightning, relative to the total
value (humans and goods) of the structure to be protected
3.1.32
risk component
R
X
partial risk depending on the source and the type of damage
3.1.33
tolerable risk
R
T
maximum value of the risk which can be tolerated for the structure to be protected
3.1.34
zone of a structure
Z
S
part of a structure with homogeneous characteristics where only one set of parameters is involved
in assessment of a risk component
3.1.35
section of a line
S
L
part of a line with homogeneous characteristics where only one set of parameters is involved in the
assessment of a risk component
3.1.36
lightning protection zone
LPZ
zone where the lightning electromagnetic environment is defined
Note 1 to entry: The zone boundaries of an LPZ are not necessarily physical boundaries (e.g. walls, floor and ceiling).
3.1.37
lightning protection level
LPL
number related to a set of lightning current parameters values relevant to the probability that the
associated maximum and minimum design values will not be exceeded in naturally occurring
lightning
Note 1 to entry: Lightning protection level is used to design protection measures according to the relevant set of lightning
current parameters.
3.1.38
protection measures
measures to be adopted in the structure to be protected, in order to reduce the risk
3.1.39
lightning protection
LP
complete system for protection of structures against lightning, including their internal systems and
contents, as well as persons, in general consisting of an LPS and SPM
3.1.40
lightning protection system
LPS
complete system used to reduce physical damage due to lightning flashes to a structure
Note 1 to entry: It consists of both external and internal lightning protection systems.
3.1.41
LEMP protection measures
SPM
measures taken to protect internal systems against the effects of LEMP
Note 1 to entry: This is part of overall lightning protection.
3.1.42
magnetic shield
closed, metallic, grid-like or continuous screen enveloping the structure to be protected, or part of it,
used to reduce failures of electrical and electronic systems
3.1.43
lightning protective cable
special cable with increased dielectric strength and whose metallic sheath is in continuous contact
with the soil either directly or by use of conducting plastic covering
3.1.44
lightning protective cable duct
cable duct of low resistivity in contact with the soil
EXAMPLE Concrete with interconnected structural steel reinforcements or metallic duct.
3.1.45
surge protective device
SPD
device intended to limit transient overvoltages and divert surge currents; contains at least one non-
linear component
3.1.46
coordinated SPD system
SPDs properly selected, coordinated and installed to form a system intended to reduce failures of
electrical and electronic systems
3.1.47
isolating interfaces
devices which are capable of reducing conducted surges on lines entering the LPZ
Note 1 to entry: These include isolation transformers with earthed screen between windings, metal-free fibre optic cables
and opto-isolators.
Note 2 to entry: Insulation withstand characteristics of these devices are suitable for this application intrinsically or via
SPD.
– 13 – EN 62305-2:2012
3.1.48
lightning equipotential bonding
EB
bonding to LPS of separated metallic parts, by direct conductive connections or via surge protective
devices, to reduce potential differences caused by lightning current
3.1.49
zone 0
place in which an explosive atmosphere consisting of a mixture of air and flammable substances in
the form of gas, vapour or mist is present continuously or for long periods or frequently
[6]
[SOURCE:IEC 60050-426:2008, 426-03-03, modified]
3.1.50
zone 1
place in which an explosive atmosphere consisting of a mixture of air and flammable substances in
the form of gas, vapour or mist is likely to occur in normal operation occasionally
[6]
[SOURCE:IEC 60050-426:2008, 426-03-04, modified]
3.1.51
zone 2
place in which an explosive atmosphere consisting of a mixture of air and flammable substances in
the form of gas, vapour or mist is not likely to occur in normal operation but, if it does occur, will
persist for a short period only
Note 1 to entry: In this definition, the word "persist" means the total time for which the flammable atmosphere will exist.
This will normally comprise the total of the duration of the release, plus the time taken for the flammable atmosphere to
disperse after the release has stopped.
Note 2 to entry: Indications of the frequency of the occurrence and duration may be taken from codes relating to specific
industries or applications.
[6]
[SOURCE:IEC 60050-426:2008, 426-03-05, modified]
3.1.52
zone 20
place in which an explosive atmosphere, in the form of a cloud of combustible dust in air, is present
continuously, or for long periods, or frequently
[4]
[SOURCE:EN 60079-10-2:2009, 6.2, modified]
3.1.53
zone 21
place in which an explosive atmosphere, in the form of a cloud of combustible dust in air, is likely to
occur in normal operation occasionally
[4]
[SOURCE:EN 60079-10-2:2009, 6.2, modified]
3.1.54
zone 22
place in which an explosive atmosphere, in the form of a cloud of combustible dust in air, is not
likely to occur in normal operation but, if it does occur, will persist for a short period only
[4]
[SOURCE:EN 60079-10-2:2009, 6.2, modified]
3.2 Symbols and abbreviations
a Amortization rate . Annex D
A Collection area for flashes to an isolated structure . A.2.1.1
D
A Collection area for flashes to an adjacent structure . A.2.5
DJ
A ' Collection area attributed to an elevated roof protrusion . A.2.1.2
D
A Collection area for flashes near a line . A.5
I
A Collection area for flashes to a line . A.4
L
A Collection area for flashes striking near the structure . A.3
M
B Building . A.2

C Location factor . Table A.1
D
C Location factor of an adjacent structure . A.2.5
DJ
C Environmental factor . Table A.4
E
C Installation factor of the line . Table A.2
I
C Annual cost of total loss in absence of protection measures . 5.5; Annex D
L
C Factor depending on shielding, grounding and isolation conditions
LD
of the line for flashes to a line . Annex B
C Factor depending on shielding, grounding and isolation conditions
LI
of the line for flashes near a line . Annex B
C Cost of loss in a zone………………………………………………………………….Annex D
LZ
C Cost of protection measures . Annex D
P
C Annual cost of selected protection measures . 5.5; Annex D
PM
C Annual cost of residual loss . 5.5; Annex D
RL
C Cost of residual loss in a zone.………………………………………………………Annex D
RLZ
C Line type factor for a HV/LV transformer on the line . Table A.3
T
c Value of the animals in the zone, in currency . C. 6
a
c Value of the building relevant to the zone, in currency . C. 6
b
c Value of the content in the zone, in currency . C. 6
c
c Total value of goods in dangerous place outside the structure, in currency ……….C.6
e
c Value of the internal systems (including their activities) in the zone,
s
in currency . C.6
c Total value of the structure, in currency . C.5; C.6
t
c Value of the cultural heritage in the zone, in currency . C.5
z
D1 Injury to living beings by electric shock . 4.1.2
D2 Physical damage . 4.1.2
D3 Failure of electrical and electronic systems . 4.1.2

h Factor increasing the loss when a special hazard is present . Table C.6
z
H Height of the structure  . A.2.1.1
H Height of the adjacent structure . A.2.5
J
i Interest rate . Annex D

K Factor
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