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Lightning Strike Protection Systems
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Lightning strike or bolt damage protection systems.

This lightning protection system website describes common lightning protection systems, certification, installation, and lightning protection system inspection. We provide information about lightning strikes, lightning hazards, related equipment, sources of lightning protection system installers, and lightning strike risk assessment.

The lightning bolt photograph at page top was taken by the author from an aircraft.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

What is Lightning, What makes lightning strike? Which way does lightning move?

House fire caused by lightning

Example of lightning-related damage to a home: This house fire in Georgia was caused by a lightning strike in April, 2008.

According to UL, "lightning is the visible discharge of static electricity within a cloud, between clouds, or between the earth and a cloud". Thunderstorms occur when warm and cold air masses meet.

[Click to enlarge any image]

Charges of electrical energy build up within the air masses and periodically discharge as energy flows from one area to another.

Upwards-moving air in the churning caused where the cold and warm fronts meet causes a separation and movement of positively-charged ions or particles to the top of clouds, leaving negative charges at the bottom of clouds.

Lightning bolts may pass vertically or horizontally between clouds or may move between the air and the ground where energy is finally dissipated.

As lightning moves towards the earth (in the form of downwards flowing negatively charged electrical energy called a "pilot leader"), positive "lightning bolts" actually move upwards from vertical features on the earth such as the edges of buildings, chimneys or trees, reaching towards along an ionized path in the air towards the downwards-moving negative energy.

It's interesting that UL says the energy moves in discrete 150' steps, ionizing a pathway in the air.

Types of Building Damage Caused by Lightning Strikes

Damaged house after fire from lightning strike

The photo above shows the extent of fire damage to the same house as the fire photo above. Damage to a home subject to a lightning strike and subsequent major fire could be expected to include:

  1. Lightning strike damage to the home - damage caused by the lightning strike itself
  2. Fire damage to the home, caused by the subsequent fire resulting from the lightning strike
  3. Water damage to the home, damage to the structure caused by water used to extinguish the fire. In this instance water contacting bricks heated by the fire may have caused additional losses.
  4. Mold contamination: risk of damage to the structure from mold growth resulting from wet conditions in any wall, ceiling, or floor cavities or surfaces which were wet during the extinguishment of the fire, if these areas were not also promptly opened, wet materials removed, and the building dried quickly.

    Our photographs of house fires caused by lightning strikes (above) were contributed by website readers.

Lightning arrestors on electrical power substation (C) Daniel Friedman

UL adds that "Scientists still do not fully understand what causes lightning but most experts believe that different kinds of ice interact in a cloud. Updrafts in the cloud separate charges so that positive charges end up at the top of the cloud while negative flow to the bottom."

Our photograph of multiple lightning arrestor masts (left) shows a lightning protection system for an electrical power substation on the Hudson River.

[Our photograph of lightning shown at page top was of strikes moving between high clouds and was taken by the author from an airplane over northern Minnesota.]

When the negative charge moves down, a pilot leader forms. This lightning strike leader rushes toward the earth in 150 discrete steps, ionizing a path in the air. The final breakdown generally occurs to a high object and the major part of the lightning discharge is then carried in the return stroke which flows along the ionized path.

What is the Amount of Energy in Lightning Strikes? What Causes Thunder?

A lightning bolt that strikes the ground, "groundstroke lightning, is producing a tremendous electrical current, around 100,000 amps. (By contrast a typical home electrical panel supports 100 to 200 amps of current to operate everything in the home).

The energy in a 100,000 amp lightning strike can in turn produce very high temperatures, up to 50,000 deg. F (this is five times hotter than the surface of the sun!). It's the rapid heating (expansion) and then cooling (contraction) of air around a lightning strike that produces the shock wave (air movement) which is heard as a thunderclap during lightning storms.

Incidentally, while lightning is normally associated with thunderstorms, lightning strikes can also be caused by erupting volcanoes, hurricanes, forest fires, and (let's hope not) nuclear explosions.

A lightning protection system does not prevent lightning from striking; it provides a means for controlling it and preventing damage by providing a low resistance path for the discharge of lightning energy. [Quotations are from UL publication 200-128C 25M/9/93]

What Are Lightning Protection Systems?

lightning protection

A lightning protection system does not prevent lightning from striking; it provides a means for controlling it and preventing damage by providing a low resistance path for the discharge of lightning energy.

But lightning protection systems have a confusing history

The earliest lightning rod design, by Ben Franklin, ended in a sharp pointed trident which may have actually created an electrical field around the tip which invited strikes.

You'll notice that modern lightning rods have a short blunt tip and that they are connected to earth by heavy metal cables, often using braided copper.

Having a properly-designed lightning protection system is very important if you're going to have one at all, since an improperly designed or installed system might actually increase the chances of a building being damaged by a lightning hit.

Lightning strikes at buildings and other sudden electrical currents (such as a tree touching a high tension power line) produce very high voltages which can take surprising routes at a property such as following underground tree roots, metal porch railings, and copper or steel building water pipes.]

 

 

How do Lightning Protection Systems Work?

lightning protectionLightning protection systems control electrical discharges by directing them through a low-resistance path to the ground, avoiding passage through parts of a structure and reducing risk of fire or other damage.

Air terminals (rods - the sketch here is of a rod tip) are fastened to the building to intercept electric discharges which might otherwise strike a building component itself, such as a chimney or metal roof.

Electrical discharges striking the air terminal are directed through heavy duty metal conductors to a grounding system (rods driven into the soil) and thence into the earth.

The lightning protection system was first invented by Ben Franklin in 1752.

 

 

 

 

Example of a Damaged Lightning Protection System

Photographs of lightning protection system components

We took these photographs of a damaged lightning protection system on an 1865 house in Orange County, New York.

The air terminal and conductor were bent down away from the top of the home leaving the chimney and roof (a metal one in an area of frequent lightning strikes) unprotected.

Photographs of lightning protection system components

This is an example of what can happen when someone who is not qualified works on the system. The lightning protection system for this home was dangerously compromised when the maintenance crew simply bent components down out of their way.

[The photographs of details of an old lightning protection system shown here were NOT the work of any of the companies or sources described at this website.]

Lightning Protection System Research & Guides

For more details on how lightning protection systems work, see

 




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Reader Question: (July 26, 2012) Deji@Imon wireless said:

Good day to you. Please we are a Vsat solutions provider. and our operations is majorly in a terrain with high Ionic Content which brings us under serious lightning and thunder attacks.

Please, i would greatly appreciate if you could advice us on what to do and if you have products that could help us, we would appreciate if you could avail us the necessary details.

Reply:

Deji, Best would be for you to search InspectApedia for "lightning protection" and you'll find all of our information there.


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