IEC 62305 - Protection against lightning
Lightning is a very high-energy phenomenon. Lightning protection is often times taken for granted as the probability of a lightning strike to a structure is low, and damage to properties and deaths due to lightning strikes are facts.
Performing lightning protection calculations according to the IEC 62305 is a little bit tricky, particularly on the risk assessment of economic losses.
As engineers don't have access to economic data at the time of the design process, inaccurate data are often used which could result in inaccurate results. In some instances, risk assessment due to economic losses is not considered at the design stage.
The IEC publication 62305 - Protection against lightning provides a comprehensive outline on how to perform lightning protection risk assessment. It has been recently updated last December 2010.
- IEC 62305-1 - Protection against lightning - General principles
- IEC 62305-2 - Protection against lightning - Risk management
- IEC 62305-3 - Protection against lightning - Physical damage to structures and life hazard
- IEC 62305-4 - Protection against lightning - Electrical and electronic systems within structures
In addition to the 4 volume publications, a risk assessment calculation software is provided free of charge.
Lightning Damage to Structures
Lightning is a high-energy electrical discharge from the atmosphere into the ground that any structure along the path of the discharge will dissipate the energy contained in it. The effects of lightning on a structure can cause damage to the structure itself and/or to its occupants and contents. The damages may also extend to the surroundings of the structure. The scale of the damage to the surroundings depends on the characteristics of the structure and on the characteristics of the lightning flash.
| Type of structure according to function and/or contents | Effects of lightning |
|---|---|
| Dwelling-house | Puncture of electrical installations, fire and material damage Damage normally limited to objects exposed to the point of strike or to the lightning current path Failure of electrical and electronic equipment and systems installed (e.g. TV sets, computers, modems, telephones, etc.) |
| Farm building | Primary risk of fire and hazardous step voltages as well as material damage Secondary risk due to loss of electric power, and life hazard to livestock due to failure of electronic control of ventilation and food supply systems, etc. |
| Theatre, Hotel, School Department store Sports area | Damage to the electrical installations (e.g. electric lighting) likely to cause panic Failure of fire alarms resulting in delayed fire fighting measures |
| Bank, Insurance company, Commercial company, etc. | As above, plus problems resulting from loss of communication, failure of computers and loss of data |
| Hospital, Nursing home, Prison | As above, plus problems of people in intensive care, and the difficulties of rescuing immobile people
Industry Additional effects depending on the contents of factories, ranging from minor to unacceptable damage and loss of production |
| Museums and archeological sites Church | Loss of irreplaceable cultural heritage |
| Telecommunications Power plants | Unacceptable loss of services to the public |
| Firework factory, Munition works | Consequences of fire and explosion to the plant and its surroundings |
| Chemical plant, Refinery, Nuclear plant, Biochemical laboratories and plants | Fire and malfunction of the plant with detrimental consequences to the local and global environment |
Source: IEC 62305-1 Protection against lightning - Part 1: General principles
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