Note: This document is still under research and may change at any time until declared closed.

Here in Florida, I am asked this regularly. In general, you cannot prevent lightning strikes. About the best you can hope for is to redirect the strike to a safer ground or minimize the direct and/or collateral damage incurred from the strike.

Although using devices such as surge suppressors are great ideas and go highly recommended, let's face facts... a $19 surge suppressor is probably not going to fare well in the face of a direct lightning strike delivering several million joules of energy¹.

Surge suppressors do offer some protection against surges (or spikes) in voltage and may, on occasion, actually offer enough electrical resistance to redirect an incidental lightning hit away from your equipment. They are better than nothing but, read this carefully... 

Don't count on that little plastic power strip to save your expensive electronics!

The bottom line in lightning protection is the bottom line. How much do you want to spend to protect your electronic equipment? A quick risk assessment will determine how much to spend on an LPS (Lightning Protection System). It may not be prudent to spend several thousand dollars to protect a $699 computer. On the other hand, if that computer contains priceless mission critical data, then installing sophisticated lightning protection and data backup equipment is probably a wise investment. 

For the typical home computer user, at the very minimum, plug all your electronic equipment into a quality surge suppressor and/or UPS². Try to build layers of protection between your equipment and the outside world. Be sure to surge protect all data and signal wires (modem, LAN, etc.) as well as power cords. If using a UPS, the correct configuration according to the IEEE (Institute of Electrical and Electronics Engineers) is: AC wall outlet to SPD (Surge Protection Device) to UPS to equipment.

Here are some facts.

Ordinary fuses and circuit breakers are not capable of dealing with lightning-induced transients³.

Whole-house meter-based surge arrestors (call your local power company or a qualified electrician) should be installed and can be very effective in reducing the risk of voltage surges across your AC power lines.

Single-point ground systems⁴ may help in redirecting lightning energy away from your home's power source, antenna, or satellite dish, but it's critical that these systems are designed and installed by a knowledgeable professional.

Lightning rods (also known as "air terminals") do not provide safety to modern electronics within structures. Lightning rods are actually designed to attract lightning and redirect it to a safe ground (usually a copper-clad steel rod embedded deep into the earth). Lightning rods have limited effectiveness and have been known to cause fires and residual damage, so be sure to investigate thoroughly before installing such systems.

There are many other exotic systems available for lightning protection of varying value. If you feel you need more effective measures, please consult a lightning protection professional.

Aside from spending many hundreds or thousands of dollars on specialized hardware, the most practical thing to do when an electrical storm approaches is to UNPLUG EVERYTHING! This is what I do, this is what you should do!

• Unplug all your equipment. This includes computers, monitors, printers, scanners and modems.
• Unplug your phone line from the dial-up or DSL modem. Electrical spikes can easily travel along telephone wires, through your modem and into your computer, wiping out everything in its path.
• Unplug the data cable from your cable-modem for the same reasons.
• Always try to unplug from the WALL end. Electrical energy can travel the wires into your home and spark out the open end possibly igniting flammable materials nearby. It can also jump the air-gap for a few inches, so don't just leave a connected power cord, wire, or cable laying near or on your equipment.
• Don't forget your other expensive electronics such as the TV, stereo, and video equipment. Even major appliances (range, refrigerator, washer/dryer, etc.) can be heavily damaged by lightning strikes.

What if I get hit?

Unfortunately, if damage occurs, you will have to have that damage replaced or repaired. Call a certified professional for a complete diagnosis and estimate of the damage. Try contacting your homeowners or renters insurance agency for reimbursement. Also, some manufacturers of surge arrest equipment offer equipment protection insurance on devices attached to their products (but be forewarned that most of these policies are very specific about what they cover and make it rather difficult to qualify for a claim).

For more important information on lightning,  lightning protection and safety, contact the National Lightning Safety Institute, the Colorado Lightning Resource Center, and select consumer manufacturers of surge suppression devices such as TrippLite, APC, and Opti-UPS. 

Good luck and stay grounded!

Notes

¹The average energy at the bottom of a lightning stroke can peak around 10 million joules. A Joule is a unit measurement of energy (Watt-seconds). For example, 100 joules is equivalent to a 100 watt light bulb that is on for one second. A single lightning strike has enough energy to light a 100 watt light bulb for 3 to 4 months.

²UPS is an acronym for Uninterruptible Power Supply. These are devices which connect between an AC wall outlet and your computer and are also known as "battery back-ups". In the event of a power failure, a UPS can safely run your computer long enough to close programs and properly shut down without data loss. A UPS usually includes surge protected outlets as well.

• Laser printers should never be plugged into the output of a UPS
• Surge suppressors should never be plugged into the output of a UPS

• On occasion, surge suppressors have been known to ignite fires when greatly overloaded. Never place a surge suppressor on or near flammable materials.

³Courtesy of National Lightning Safety Institute.

⁴A single point grounding system is where all of the equipment within a structure is connected to a master bus bar which in turn is bonded to an external grounding system at one single point.

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