Lightning Protection Systems
Lightning is a very powerful force, producing millions of volts of energy – as much as 150,000 amperes – with every strike. Sometimes lightning strikes the ground; other times it takes a detour to the ground through a tree, an antenna tower or a building.
When lightning takes such a detour, its extremely high voltage and currents create so much heat as they travel through conductive paths that they can destroy electrical systems, ignite structures, or cause explosions. A lightning protection system minimizes damage by diverting strikes using lightning rods or other kinds of air terminals. Once lightning strikes the air terminal, lightning protection systems then direct the current through properly installed conductive paths into the earth.
There are three effective types of air terminals designed to intercept lightning strikes:
- Traditional lightning rods are copper or aluminum rods that provide a highly conductive path to ground during thunderstorms.
- Early streamer emission (ESE) terminals send out upward streamers (the branch of lightning that rises from the ground to the cloud) to meet any downward leaders (the branch of lightning that extends from the cloud).
- Dissipation technology acts on the electrostatic field present on the ground when thunderclouds form in an attempt to prevent the formation of upward streamers.
The interception and redirection of the lightning strike is only part of a complete system. The low-impedance components that carry lightning voltage and currents to the ground are:
- Downconductors, made out of flat or braided copper or aluminum. As the name implies, they conduct energy down from the air terminal toward the ground. How downconductors are routed during installation can also reduce the possibility of side-flashing, which is when lightning jumps from its initial strike point.
- Ground rods, also made out of copper, are buried at the base of the downconductors. They absorb and disperse the energy safely into the earth. Even soil conditions can affect the type of grounding system installed.
All of the connections from the air terminal to the ground rod are electrically bonded to create a path of least resistance.
A lightning protection installation might use just one type of air terminal, while other systems require a combination of technologies. Proper integration and electrical bonding between the components is absolutely critical and should adhere to standards.