IEC 62305 classifies lightning damage with three items: the source (S1 to S4, according to the point of strike), the type of damage (D1 electric shock to living beings, D2 physical damage, D3 failure of electrical and electronic systems) and the loss (L1 human life, L2 public service, L3 cultural heritage, L4 economic value). A strike near the structure or near a line can only cause D3.
Short answer
IEC 62305-1 describes lightning damage with three linked classifications. The source depends on where the lightning strikes: S1 on the structure, S2 near it, S3 on a connected line, S4 near a connected line. The type of damage can be D1 (electric shock to living beings), D2 (physical damage) or D3 (failure of electrical and electronic systems). The loss can be L1 (loss of human life), L2 (loss of service to the public), L3 (loss of cultural heritage) or L4 (loss of economic value).
The four sources of damage
The lightning current is the source of damage. The standard classifies it by the point of strike:
| Source | Where the lightning strikes | Damage it can cause |
|---|---|---|
| S1 | The structure | Mechanical damage, fire or explosion from the arc and from conductor heating; sparking from overvoltages; electric shock to people from step and touch voltages; failure of internal systems from the electromagnetic impulse |
| S2 | Near the structure | Failure or malfunction of internal systems from the electromagnetic impulse |
| S3 | A line connected to the structure | Fire or explosion from sparking, shock from touch voltage inside the structure and failure of internal systems from overvoltages traveling along the line |
| S4 | Near a connected line | Failure of internal systems from overvoltages induced in the line |
By «line» the standard means a power or telecommunication line connected to the structure. A power line feeds electrical and electronic equipment inside, at low or high voltage; a telecommunication line links equipment that may be in different structures, such as a telephone or data line.
The overvoltage from a nearby strike reaches the equipment through the cables even if the lightning did not touch the building. For that reason a control room with air-termination on the roof is still exposed to S2, S3 and S4.
The three types of damage
- D1: electric shock to living beings. Permanent injury, including death, from step and touch voltages. The standard limits this term to electric shock, although a living being may be injured in other ways.
- D2: physical damage. Fire, explosion, mechanical destruction or release of chemical substances caused by the effects of the lightning current, including sparking.
- D3: failure of internal systems. Permanent damage to electrical and electronic systems caused by the lightning electromagnetic impulse (LEMP). Mere malfunction, without permanent damage, is not covered by the series.
The four losses
- L1: loss of human life, including permanent injury.
- L2: loss of service to the public. The standard considers public service to be only gas, water, television, telecommunications and power supply.
- L3: loss of cultural heritage.
- L4: loss of economic value: the structure, its contents and the activity.
L1, L2 and L3 are losses of social value. L4 is purely economic.
How they relate: the table in the standard
| Point of strike | Source | Damage | Possible losses |
|---|---|---|---|
| Structure | S1 | D1 | L1 and L4 (L4 only where animals can be lost) |
| D2 | L1, L2, L3 and L4 | ||
| D3 | L1, L2 and L4 (L1 only in structures with an explosion risk and in hospitals or others where failure of internal systems immediately endangers life) | ||
| Near the structure | S2 | D3 | L1 (in the same cases), L2 and L4 |
| Connected line | S3 | D1, D2, D3 | Same as S1 |
| Near a line | S4 | D3 | Same as S2 |
This means D2 is the damage with the most possible consequences, and D3 is the only one that can come from all four sources.
Effect by type of structure
Table 1 of Part 1 summarizes the typical effects. Some examples useful for those working in power and industry:
- Power and telecommunication plants: unacceptable loss of service to the public.
- Industry: additional effects depending on the contents, from minor damage to unacceptable loss of production.
- Hospitals, care homes and prisons: in addition to the effects for offices and banks, problems for people in intensive care and difficulty rescuing those who cannot move.
- Chemical plants, refineries and nuclear plants: fire and plant malfunction, with consequences for the local and global environment.
- Fireworks and ammunition factories: fire and explosion in the plant and its surroundings.
The effect depends on the characteristics of the structure: construction, function, occupants and contents, connected lines, existing protection measures and the extent of the hazard, for example whether evacuation is difficult or the surroundings are at risk.
What this classification is for
Each type of loss generates a risk that is calculated and compared with a tolerable value. R1 corresponds to loss of life, R2 to public service, R3 to cultural heritage and R4 to economic value. The classification decides which components enter each risk, and the calculation is made with Part 2 of the standard, which is covered in the guides on risk management and risk components.
The same logic guides the measures. Part 1 assigns different measures to each type of damage: insulating exposed parts and equipotentializing the ground against D1, a lightning protection system against D2, and LEMP measures (shielding, cable routing, isolating interfaces and coordinated SPDs) against D3.
Guides in the same series
Losses are turned into risk with the method in lightning risk management. The division of the structure into zones is covered in lightning losses LX, and the interior boundaries that reduce damage in LPZ protection zones.
When to contact us
If you need to know which damage and losses apply to your control building, plant or substation, write to us with the type of structure and the lines that feed it. Learn about our engineering design and studies service and write to us through contact.
Related guides
- IEC 62305 lightning protection: what each part covers
- Lightning risk management: when protection is needed
- Lightning risk components in IEC 62305-2: RA to RZ
- Lightning losses LX and division of the structure into zones
- Transient overvoltages in the plant
References
- IEC 62305-1:2010, Protection against lightning – Part 1: General principles, clauses 3.31 to 3.35, 5.1 and 5.2 (tables 1 and 2) and 7.
- IEC 62305-2:2010, Protection against lightning – Part 2: Risk management, clause 4.1 (table 1) and clauses 4.2.2 to 4.2.5.
Frequently asked questions
Can a lightning strike far from the structure damage its equipment?
Yes. Sources S2 and S4 are strikes near the structure or near a connected line. They cause damage type D3, failure of electrical and electronic systems, through the overvoltages that the electromagnetic impulse induces in the structure or in the lines.
Is a strike on a metal pipe entering the building considered a source of damage?
No, provided the pipe is bonded to the structure's equipotential bonding bar. The standard states this in the notes to clause 5.1.2 of Part 1 and clauses 4.2.4 and 4.2.5 of Part 2; if there is no bonding bar, that threat must be considered.
What is the difference between damage and loss?
Damage is what physically happens to the structure: electric shock to a living being, fire or equipment failure. Loss is the consequence of the damage: human life, public service, cultural heritage or economic value. A single damage can cause several losses.