Lightning Strike Damage and Losses – IEC 62305

IEC 62305 identifies four main sources of damage:

1. S1 Flashes to the structure
   • mechanical damage, fire and/or explosion due to the hot lightning plasma arc, over-heated conductors or melted metal;
   • fire and/or explosion triggered by sparks;
   • injury to living beings by electric shock;
   • failure or malfunction of internal systems due to Lightning Electromagnetic Pulse (LEMP).
2. S2 Flashes near to the structure
   • failure or malfunction of internal systems due to LEMP.
3. S3 Flashes to a service
   • fire and/or explosion triggered by sparks;
   • injury to living beings by electric shock;
   • failure or malfunction of internal systems due to overvoltages.
4. S4 Flashes near to a service
   • failure or malfunction of internal systems due to overvoltages induced on connected lines and transmitted to the structure.

Each source of damage may result in one or more of three types of damage:

1. D1 – Injury of living beings due to step and touch voltages
2. D2 – Physical damage (fire, explosion, mechanical destruction, chemical release) due to lightning current effects including sparking
3. D3 – Failure of internal systems due to Lightning Electromagnetic Impulse (LEMP)

The following types of loss may result from damage due to lightning:

1. L1 – Loss of human life
2. L2 – Loss of service to the public
3. L3 – Loss of cultural heritage
4. L4 – Loss of economic value

Losses of type L1, L2 and L3 may be considered as loss of social values, whereas a loss of type L4 may be considered as purely an economic loss.

The relationship between source of damage, type of damage and loss is reported in Table 1.

Table 1: Damage and loss in a structure according to different points of lightning strike (IEC 62305-1 Table 2)

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.