Lightning Strike Information

What is the typical amperage and voltage levels in a cloud to earth lightning strike?

Lightning bolts range from 5,000 Amperes to 200,000 Amperes and voltages vary from 40,000 Volts to 120,000 Volts. kV to 120 kV. So, depending on the amperage and voltage level when it passes over these objects and what those objects are attached too will determine if any electronic or digital equipment will be damaged.

How far away from a lightning strike is your electronic and digital equipment safe?

When a lightning strike to earth takes place the strike point voltage level rises to the level delivered from the lightning bolt. The voltage and current from that strikes then races across the earth in all directions dissipating the voltage until it reaches a point of zero voltage. Your electronic and digital equipment are not 100% safe until your facility reaches a zero-earth voltage level. Depending on the resistance of the soil this voltage and current could take up to nine (9) miles in all direction (254.34 Square Miles) to reach zero voltage.

What happens when lightning voltages travel across the earth?

1. Lightning voltages travel across the earth in all directions seeking its own voltage return path until it reaches zero volts.
2. It will travel on all conductive paths such as metallic pipes, underground wires, and all metallic paths.
3. These metallic paths are usually a less Ohmic resistance value than soil so that when the voltage and amperage divides, a great amount of voltage and current will travel on those devices seeking its return path.
4. This, is called Ground Potential Rise or Earth Potential Rise.
5. Because all facilities with electrical service require grounding this lightning voltage and amperage now has a direct path from earth into the facility and its electrical equipment via the grounding systems.
6. Most Ac electrical equipment in the USA works off of 120, 208, 240, 277 or 480 volts. Depending on the voltage safe operating levels of the equipment the closer distance from the lightning strike the more susceptible the equipment is to failing from this excess voltage.
7. Most Dc electrical equipment in the USA works off of 5 to 48 volts. Depending on the voltage safe operating levels of the equipment the closer distance from the lightning strike the more susceptible the equipment is to failing from this excess voltage.

How far in advance of a storm front can lightning strike?

Typical lightning can strike 5-10 miles ahead of the storm front however; anvil lightning can strike hundreds of miles ahead of a storm front. Sometimes anvil lighting is referred to as lighting from out of the blue.

How far away can a person see a typical storm front?

For an average person with an eye level of 5 feet 7 inches the horizon is at a distance of 2.9 miles. For an average person with an eye level of 5 feet 7 inches standing on a 100-foot hill the horizon is at a distance of 12.2 miles.

How can electrical equipment be protected from a ground potential rise?

A facility needs to be properly grounded and surge protection needs to be properly installed for the Ac service, Telephone lines, Data lines, Coaxial cables, CCTV, CATV, Antenna systems, Radio systems, ets. In addition, all ground loops for voltage sucepticable equipment must be eliminated.

How can I protect my building and electrical equipment be protected from a Lightning strike?

A properly installed Lightning Protection System (LPS) must be installed. This is in addition to the protection requirements from a ground potential rise.

 What are my main risks from a lightning strike?

• Inside the Home
  • Contact with metallic objects
  • Talking on a telephone land line
  • Contact with water
  • Side flash from metallic lined chimney
• Outside the home
  • Direct strikes
  • Side flash from a lightning strike to a nearby object
  • Ground potential rise from a nearby lightning strike
  • Contact with metallic objects
  • Contact with water
  • Being in an open field during a lightning storm

 What is my facility’s risk from a lightning strike?

Below is a table that shows the average lightning strikes per year by state. Please note that the average strikes per square mile are not necessary the state with the most lightning strikes.