Introduction:
A lightning strike is a natural phenomenon of sudden discharge of charges from a highly concentrated cloud or any object. Lightning cannot be avoided, rather the damages can be reduced with proper preventive measures. The complete protection includes a properly designed and executed external and internal lightning protection system.
Lightning Protection System:
The designing of a lightning protection system can be divided into 2 major parts,
1. Risk assessment
2. Designing
Risk assessment:
Risk assessment measures the risk due to lightning strikes and the probability of damages. IS/IEC 62305 -2 explains the damages due to lightning strikes, the source of such damages, losses due to lightning and the corresponding risks.
The damages caused by the lightning strike as specified in IS/IEC 62305 part 2 are as follows.
1) Loss of human life / Injury (D1)
2) Physical damage (D2)
3) Electrical /Electronic components (D3)
We have already explained about the sources of damages, losses, risks and risk components in our previous articles.
Design of lightning protection system:
IS/IEC 62305 -3 has given the procedure for designing lightning protection for both external as well as internal system.
- Lightning design shall be done with respect of class of lightning protection system.
- The position of the air termination system shall be designed by using the following placement methods as specified by IS/IEC 62305-3
1) Protection Angle Method
2) Rolling Sphere Method
3) Mesh Method
- The distance between down conductors will depends on the class of lightning protection.
- IS/IEC 62305 has given the arrangement of earth termination system.
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