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Guide to BS EN/IEC 62305 BS EN/IEC 62305-1
Damage and loss
BS EN/IEC 62305 identifies four main sources of
damage:
S1 Flashes to the structure
S2 Flashes near to the structure
S3 Flashes to a service
S4 Flashes near to a service
Each source of damage may result in one or more of
three types of damage:
D1 Injury of living beings due to step and
touch voltages
D2 Physical damage (fire, explosion, mechanical
destruction, chemical release) due to lightning
current effects including sparking
D3 Failure of internal systems due to Lightning
Electromagnetic Impulse (LEMP)
The following types of loss may result from damage
due to lightning:
L1 Loss of human life
L2 Loss of service to the public
L3 Loss of cultural heritage
L4 Loss of economic value
The relationships of all of the above parameters are
summarised in Table 5.
Figure 12 on page 271 depicts the types of damage
and loss resulting from lightning.
For a more detailed explanation of the general
principles forming part 1 of the BS EN 62305 standard,
please refer to our full reference guide ‘A Guide to
BS EN 62305.’ Although focused on the BS EN
standard, this guide may provide supporting
information of interest to consultants designing to the
IEC equivalent. Please see page 283 for more details
about this guide.
Scheme design criteria
The ideal lightning protection for a structure and its
connected services would be to enclose the structure
within an earthed and perfectly conducting metallic
shield (box), and in addition provide adequate
bonding of any connected services at the entrance
point into the shield.
This in essence would prevent the penetration of the
lightning current and the induced electromagnetic
field into the structure.
However, in practice it is not possible or indeed cost
effective to go to such lengths.
This standard thus sets out a defined set of lightning
current parameters where protection measures,
adopted in accordance with its recommendations, will
reduce any damage and consequential loss as a result
of a lightning strike. This reduction in damage and
consequential loss is valid provided the lightning strike
parameters fall within defined limits, established as
Lightning Protection Levels (LPL).
BS EN/IEC 62305-1 General principles
This opening part of the BS EN/IEC 62305 suite of standards serves as an introduction to the further parts
of the standard. It classifies the sources and types of damage to be evaluated and introduces the risks or
types of loss to be anticipated as a result of lightning activity.
Furthermore, It defines the relationships between damage and loss that form the basis for the risk
assessment calculations in part 2 of the standard.
Lightning current parameters are defined. These are used as the basis for the selection and
implementation of the appropriate protection measures detailed in parts 3 and 4 of the standard.
Part 1 of the standard also introduces new concepts for consideration when preparing a lightning
protection scheme, such as Lightning Protection Zones (LPZs) and separation distance.
Point of strike Source of
damage
Type of
damage
Type of
loss
Structure S1 D1
D2
D3
L1, L4**
L1, L2, L3, L4
L1*, L2, L4
Near a
structure
S2 D3 L1*, L2, L4
Service
connected to
the structure
S3 D1
D2
D3
L1, L4**
L1, L2, L3, L4
L1*, L2, L4
Near a service S4 D3 L1*, L2, L4
* Only for structures with risk of explosion and for hospitals or other
structures where failures of internal systems immediately endangers
human life.
** Only for properties where animals may be lost.
Table 5: Damage and loss in a structure according to different points of
lightning strike (BS EN/IEC 62305-1 Table 2)