Lightning facts

What is lightning?

Lightning travels at over 140,000 mph and is hotter than the surface of the sun. Most lightning discharges harmlessly in the atmosphere, but lightning bolts still strike the Earth over 100 times a second and each bolt can contain over 1 billion volts of electricity. If lightning strikes a building, it can cause considerable direct and indirect damage and even loss of life.

Ground Strike

This enormous electrical discharge is caused by an imbalance between positive and negative charges. During a storm, massive storm clouds gather (the biggest can be up to 75,000 feet high). Within these clouds, convection causes air to rise and fall, colliding particles of rain, ice or snow together. The static created causes an imbalance and often negatively charge the lower reaches of storm clouds whilst positively charging the top of the cloud. Objects on the ground, like steeples, buildings, and the Earth itself, become positively charged. Nature tries to remedy this imbalance by passing current between the two charges – either within the cloud or from cloud to Earth.

The instantaneous movement of electrons between the two charged areas is seen as a brilliant flash of light. The heat generated by this exchange of electrons causes the air to rapidly expand and then contract. This physical movement of air is heard as a loud noise, we call thunder. The total effect on any object subject to or in the vicinity of such a discharge can be any or a combination of thermal, electrical and mechanical.

Continual dry air movement over the ground gives rise to a charge forming over a large area. The occasional equalisation or discharge from an invisible cloud or charge centre is known as ‘a bolt from the blue.'

Studies with high-speed cameras have shown that most lightning flashes are multiple events, consisting of as many as 42 main "strokes" of lightning, each of which is preceded by a "leader" stroke. These leaders are areas where charged ions are collecting in the atmosphere. All strokes follow an initial ionized path, which may be branched, along with the current flows. The average interval between successive lightning strokes is 0.02 sec and the average flash lasts 0.25 sec.

Striking Facts About Lightning

  1. The irrational fear of lightning (and thunder) is astraphobia. The study or science of lightning is called fulminology
  2. The old saying that lightning never strikes twice is absolute nonsense. Lightning occurs frequently and more so in specific areas.
  3. If lightning strikes a property either directly or secondarily, it has done so because the property and its contents are vulnerable to lightning strike and therefore unless that vulnerability is removed or protected it will strike again and again.
  4. To fully protect a building from direct lightning, a comprehensive lightning protection system is required combining copper and/or aluminium tapes with an earthing system.
  5. Tapes are fitted to a building in the form of a “Faraday Cage” and as such can be fitted either on the surface of the building or fitted under the tile or behind surface cladding.
  6. In modern buildings, where steelwork is utilised either as a structural form encased in brick and tile, or encased in metallic sheeting, the steelwork itself can be utilised as conductors for the system.
  7. If surface mounted tapes are utilised these can be fitted with colour matching pvc sheathing to blend in with the building materials and therefore become more aesthetically acceptable.
  8. In addition to the structural damage caused by a lightning strike, secondary lightning strikes can cause serious permanent damage to electronic equipment within a building.
  9. Lightning can strike the ground up to a kilometre away from a building and travel via underground cables and services and ultimately damage or destroy electronic equipment.