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Lightning Protection Systems Information and Sources of Lightning Protection Systems

  • LIGHTNING PROTECTION SYSTEMS - CONTENTS: What is lightning, where and why does lightning strike?Example of lightning and lightning-related fire damage to a home. What are lightning protection systems ? How do lightning rods work? Design specifications for lightning protection systems (basic). How to inspect lightning protection systems. Where to buy lightning protection systems & equipment. What is the chance of being struck by lightning? What happens? How to avoid being struck by lightning. Lightning Strikes Small Boat on Rappahannock River - photos
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Lightning stricke or 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.



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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]

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Continue reading at LIGHTNING PROTECTION SYSTEMS, DEFINITIONS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see BUILDING SAFETY HAZARDS GUIDE

Or see GAS PIPING, FLEXIBLE CSST for a discussion of lightning protection needed for flexible stainless steel tubing used as gas piping

Or see these Lightning Strike Protection System Articles

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