Lightning Protection in Buildings

Necessity of lightning protection system:

• Lightning is one of nature’s most powerful & destructive phenomena.
• It contains a huge amount of energy (several thousands of Amps)
• It is a short duration ( up to 200 µsec ) but is a real cause of damage & destruction
• Primary effect- Buildings damaged, trees blown, personal injuries and even death
• Secondary effect- Transient overvoltage- damage to electronic system
• It can also cause fire, explosion, chemical release or mechanical disruption within or around a bldg.

Lightning Protection System (LPS)

• The lightning rod (Rod is earthed by one or more conductors)
• The lightning rod with taut wires (stretched above structure)
• Lightning conductor with meshed cage/Faraday cage (numerous down conductors & tape symmetrically placed)

Standards:

• BS 6651
• NFPA 780
• BS-EN/IEC 62305
• In Aug. 2008, BS 6651 has been withdrawn
• Now IEC 62305 & NFPA 780 are the recognised standards for LPS

Elements of a Lightning Protection System (LPS)

1. Air Termination System (Arrestor)

• Arranged at or along upper points of a roof
• Used to capture lightning current
• Dissipate it harmlessly to earth
• Material- Copper, Aluminium
• It consists of base, air rods & multiple points
• 25*6 mm Al tape on surface interconnected through clips and clamps (fig. 1…