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Source of damage S1 S2 S3 S4
Lightning strike Lightning strike Lightning strike to an Lightning strike
to a structure near a structure incoming line near an
Type of damage incoming line
D1: Injury of living beings due
to electric shock R = N D P L A R = (N + N ) P L U
L
A
U
A
DJ
U
D2: Physical damage R = N D P L B R = (N + N ) P L V
B
B
V
V
DJ
L
D3: Failure of electrical and R = N P L R = (N + N ) P L R = N P L
electronic systems C D C C R = N M P M L C W L DJ W W Z I Z Z
M
R = R + R + R C R = R + R + R + R + R Z
d
V
W
M
i
B
U
A
Note: For risk components R U , R V and R W , not only the frequency of direct lightning strikes to the line N L are important, but also the frequency
of direct lightning strikes to the connected structure N DJ (see Figure 3.2.3.3)
Table 3.2.6.1 Risk components for different points of strike (sources of damage) and types of damage
L FE should be provided by the body preparing the explosion Type of loss R T (1/year)
protection documents.
L1: Loss of human life or permanent injury 10 -5
L2: Loss of service to the public 10 -3
3.2.6 Relevant risk components for different L3: Loss of cultural heritage 10 -4
types of lightning strikes L4: Loss of economic value (only IEC 62305-2) 10 -3
There is a close correlation between the type of damage, the
type of loss and the resulting relevant risk components. De- Table 3.2.7.1 Typical values for the tolerable risk R T
pending on the sources of damage S1 to S4 (or on the point
of strike), there are the following risk components (Table R d Risk due to a direct lightning strike to a structure (S1);
3.2.6.1): R i Risk due to all indirect lightning strikes related to a
structure (S2 to S4);
In case of a direct lightning strike to a structure (S1):
R A Risk of injury to living beings caused by electric shock;
R B Risk of physical damage; 3.2.7 Tolerable risk of lightning damage
R C Risk of failure of electrical and electronic systems. When selecting lightning protection measures, it must be ex-
amined whether the risk R determined for the relevant types
In case of a lightning strike to the ground near a structure (S2): of loss exceeds a tolerable value R T . For a structure which is
sufficiently protected against the effects of a lightning strike
R M Risk of failure of electrical and electronic systems
we have:
R R
In case of a direct lightning strike to an incoming line (S3): T
R U Risk of injury to living beings caused by electric shock; Table 3.2.7.1 shows the values of R T listed in IEC 62305-2
R V Risk of physical damage; (EN 62305-2) for these three types of loss.
R W Risk of failure of electrical and electronic systems
In case of a lightning strike to the ground near an incoming 3.2.8 Selection of lightning protection
line (S4): measures
R Z Risk of failure of electrical and electronic systems. Lightning protection measures are supposed to limit the risk R
to values below the tolerable risk R T . By using a detailed calcu-
The eight risk components can also be defined according to lation of the risks for the relevant types of loss and by classify-
the point of strike: ing them into the individual risk components R A , R B , R C , R M ,

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