Lightning

1
Lightning

• ASM 4140

2
Nature of Lightning

• Negative charges in lower clouds
• Positive charges on ground
• Initially negative charge travels to ground
• A shorter leader travels to cloud
• When these meet 100,000 AMPS!
• Temperature 27,500 degrees C
• 1.3 billion hp for 100 microseconds

3
Lightning Protection

• Cannot be prevented
• Direct strike to a building
• Direct strike to a tree or pole that damages the
  building
• Induced into the electrical system
• Surge suppressors protect electrical TV, etc.

4
Protecting Buildings

• Air terminals
• Main conductors
• Branch conductors bond metal to mains
• Earth grounding electrode
• Secondary lightning arresters
• Common Grounding

5
Protection

• Trees
• Livestock
• Ground wire fences wood posts
• 5 foot rod
• 150 feet (can travel in excess of 200
• Risk assessment for buildings p. 372

6
Personal Protection

• Lightning strikes 100 places every second
• 100-200 people die each year in the US
• No one hit by lightning survives
• 100,000 AMPS at little at .02 AMPS kills
• If hit directly, lightning will stop your heart,
  boil all the water in your body, and instantly
  kill you.

7
Personal Protection

• You become an air-core Transformer
• The tree Is ½ of the transformer
• You are the other ½, so current is induced into
  your body!
• Use the Desperation Position

8
Personal Protection Dont

• Stand near a tree
• Stand near a window
• Golf in the rain
• Use a wired phone
• Stand near a TV
• Get out of your car (keep hands away from steel)
• Take a shower or work in or near a sink

9
Boating

• Problems with small open boats get to shore!
• Caught in a large boat, anchor the boat and go to
  the cabin
• Crouch in the desperation position in the center
  of the cabin
• Keep OFF the radio
• If you have scuba gear, get UNDER water

10
Lightning protection for a boat

• Terminal Antenna
• 8 copper to the water
• Metal plate in water at least 1 foot square