By intercepting lightning strikes and safely passing their extremely high currents to the ground, a modern lightning protection systems help prevent structures from being damaged by lightning strikes. Lightning protection systems use an interconnected network of air terminals, bonding conductors, and ground electrodes to provide low impedance paths to the ground in case of potential strikes.
Modern Lightning protection systems are used to prevent damage from lightning strikes on structures. Structures are protected from the fire hazard caused by lightning strikes with modern lightning protection systems. Lightning protection systems reduce the heating effect of current flowing through flammable structural materials by providing low-impedance paths for lightning current. Lighting traveling through porous and water-saturated materials may cause the materials to explode if the heat generated by the high current converts the water into steam. For this reason, trees are often shattered by lightning strikes.
Because lightning has high current and energy levels (currents can be more than 150,000 amps), and because lightning strikes rise very rapidly, no lightning protection system guarantees absolute safety from lightning strikes. Any conductive path to ground will split lightning current, and even the divided current can cause damage. There are secondary impacts that can ignite a fire, rip apart bricks, stone, and concrete, or cause injury to occupants within a structure or building. It has, however, been evident for nearly a century that modern lightning protection systems offer significant advantages.
There are four main parts to a lightning protection system: air terminals (lightning rods or strike termination devices), bonding conductors, ground terminals (ground metal rods, plates, or mesh), and the connectors and supports. There are typically air terminals located near the tops of roof structures, which are connected electrically by bonding conductors (called “down conductors” or “downleads”), which are connected via one or more grounding or earthing terminals. The earth electrode connections must not only have low resistance, but also low self-inductance.
Many of the traditional and modern lightning protection systems used today are of the Franklin design. A Franklin-type lightning protection system works by providing a sufficiently low impedance path for lightning to travel through in order to reach the ground without damaging the building. The building is surrounded by a Faraday cage to achieve this. To prevent lightning from striking the building, lightning rods and conductors are installed on the roof.