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LIGHTNING Lightning a high voltage electrical discharge between two charged rain clouds or a cloud & the earth,

h, caused by build up of electrical charge. Air is the path of lightning ionizes (becomes conducting), and expands. The sudden expansion of air causes thunder. Lightning produce currents of 20,000 A & temperature of 30,000C Lightning Arrestors Device that protect a tall building by providing an easier path for current to flow to earth than through the building. Consists of a thick copper strip, a huge metal plate buried in the damp earth. If direct lightning strike, the current flows through the conductors & melting or even vaporize the metal. Therefore the building is safe. Lightning strikes are electrical discharges caused by lightning, typically during thunderstorms. A lightning rod (or lightning protector) is a metal strip or rod, usually of copper or similar conductive material, used as part of lightning safety to protect tall or isolated structures (such as the roof of a building or the mast of a vessel) from lightning damage. Its formal name is lightning finial or air terminal. Sometimes, the system is informally referred to as a lightning conductor, arrester, or discharger; however, these terms actually refer to lightning protection systems Damage to electrical equipment Telephones, modems, computers and other electronic devices can be damaged by lightning, as harmful overcurrent can reach them through the phone jack, Ethernet cable, or electricity outlet. A secondary effect of lightning on users of telephone equipment can be hearing damage, as the strike may cause bursts of extremely loud noise. Close strikes can also generate electromagnetic pulses (EMPs) - especially during 'positive' lightning discharges. If a person is injured by lightning they do not carry an electrical charge and can be safely handled to apply first aid before emergency services arrive. Lightning can affect the brainstem, which controls breathing. If a victim appears lifeless, it is important to begin artificial resuscitation immediately to prevent death by suffocation

Lightning Arrestors are needed: 1. stormy area where possibility of lightning strikes is frequent. 2. structures at hilly or high area (telecommunication tower). 3. structures that more than 53m high (pylon) 4. structures & its contents are sensitive/highly prices (fuel tanks or electronic factories) Lightning Protection Key:

1. 2. 3. 4.

Minimum of two ground rods (electrodes) at least 10 feet deep. Down conductors. Connect gutters or other grounded metals as required. Air terminals (lightning rods) located within two feet of outside corners of chimney. 5. Antenna must connected to roof conductor. 6. Air terminals (lightning rods) spaced 20 feet apart along the ridges and within two feet of ridge ends. 7. Dormers protected. 8. Roof projections such as weather vanes or satellite dishes should be connected to lightning protection system. 9. Surge protection devices installed at main electrical panel or meter. 10. Surge protection devices installed at electronics in house.