Lighting Strikes: a Bolt From the Blue Page 2

Had I been desperate and/or gullible enough to be talked into buying a new computer, add $800–$1600. Then figure in the hours of hassling with service people and salesmen. An obvious question at this point is, "Why didn't you make an insurance claim?" The answer is that I had let our policy lapse and had been "too busy" to call our agent. Human oversights and mistakes can combine with natural disasters to yield costly, and sometimes deadly, results.

I had hoped, in researching this article, to produce some "shocking" statistics regarding the dollar value of electronic products damaged or destroyed by lightning each year. No one I talked to tracks such statistics, not the Electronic Industries Association, the National Fire Protection Association, the Lightning Protection Institute or, most curiously, the insurance industry itself.

What I did discover is that a couple hundred people are killed by lightning each year (most of them in open areas such as golf courses), thousands are injured, and countless fires are started. Should you be caught outdoors in a thunderstorm, do not seek shelter under isolated trees or ungrounded outbuildings. Find the lowest spot nearby and get down in it. That means kneeling in a sand trap if necessary; dirty, wet, and alive is usually preferable to clean, dry, and dead. If you're indoors, avoid putting yourself between any source of current and ground; a friend of mine was knocked unconscious while talking on the telephone during an electrical storm when she touched a faucet in her kitchen. (Complete instructions for protecting yourself from a lightning flash are available free from the LPI.)

Lightning is associated with all kinds of atmospheric disturbances, from snowstorms and sandstorms to volcanic eruptions. On rare occasions the electrical charge in clear air may be sufficient to prompt a discharge to ground—the proverbial "bolt from the blue." Ordinarily, lightning flashes occur during thunderstorms and move from cloud to air, from cloud to cloud, within a cloud, or from cloud to ground. About 90% of all lightning is this last type and, naturally, causes damage such as I experienced.

The physiology of the electrical storm is a fascinating subject in itself and follows this oversimplified scenario: warm, moist air rises, either locally, in convection currents, or regionally, in storm fronts, pushed aloft by incoming cold fronts. As the moist air rises it begins to cool and the water vapor it contains condenses to form water droplets and ice particles. Turbulence within the cloud causes friction between upward-moving light particles and downward-moving heavy ones; this friction results in the buildup of regions of static space charge within the cloud—positive above, negative below. The greater the initial moisture and the more turbulent the cloud, the higher the static charge. After a developmental period the charge may reach a potential of several million volts, enough to overcome the insulating property of thousands of feet of air between it and the ground. A fully charged stormcloud cruises above the earth, inducing an electrical "shadow" of opposite polarity. The cloud is "looking" for a place to discharge.

The exact relationship between rain and lightning is not understood; while they frequently accompany each other, it's possible, even likely, to have one without the other. (You may appreciate the difficulty of conducting controlled experiments within stormclouds.) What is understood is that an event called a breakdown pulse, not unlike the biasing-on of a semiconductor, produces a leader which reaches tentatively toward ground in a characteristic zigzag fashion, each step about 50 yards long and about one microsecond in duration. The leader does not have a specific target; it moves blindly until it is within a critical radius of ground known as the striking distance. At this point an upward-moving discharge meets it; a conduction channel is formed and a return stroke surges thousands of amperes through it.

Imagine the two poles of a high-voltage transmission line being shorted together. The mightiest power amplifiers, with peak current capabilities of 50 amps or so, are pitiful pipsqueaks compared to Mother Nature. A lightning flash may consist of several strokes, each about 50µs long, with successive strokes reaching higher into the cloud to lower its charge. Persistence of vision, the ocular phenomenon which makes the individual frames of a film merge into continuous action, prevents us from seeing individual strokes. The superheated ionized gas of the conduction channel explodes as a shockwave, which quickly decays into an acoustic wave, which we hear as thunder, but only at a distance from the flash—lightning striking nearby makes a sharp cracking sound, like a rifle shot or the breaking of a branch.

The geographical distribution of lightning is greatest in humid subtropical or tropical climates, and is at maximum near the equator. A day when thunder occurs is known in meteorological jargon as a "thunderstorm day"; central Florida is the North American champ, with over 90 per year. Lightning is common throughout the southeast, especially along the coasts, striking 60 to 70 days per year. The midwest is no stranger to it either, with occurrences in the 40–50 range. The Rocky Mountain region is the most electrically active area in the west, with one curious exception: northeastern New Mexico, which experiences lightning an average of 60 days per year. The west coast, from British Columbia to Mexico, is relatively free from lightning, with an average of only five strikes per year.

Lightning will surge through almost anything in its path: trees, fishermen, and circuit boards alike. Merely switching your equipment off is an act of faith at best; lightning which has arced a mile or two through the air will not be deterred by a quarter-inch gap between the contacts of a power switch. Fuses won't help much either; even the fastest fast-blow fuse will let a high-energy pulse through before it opens. When you anticipate an electrical storm, you must disconnect everything from wall outlets, cable feeds, and telephone lines. Outlet strips simplify disconnecting AC. Cable connections can be made easier by installing push-on adapters (Radio Shack part #278–218) to standard "F" fittings on 75 ohm coax.

What do you need to do to protect your home and its contents? First you need to assess the likelihood of your being struck. If you live in a crowded urban area you're probably safer than you are in the suburbs or the country. If you live in a steel-framed high-rise, please turn to the equipment reports or music reviews, because the National Electrical Code, your building's architect, and your local electrical inspectors have conspired for your safety. Should lightning strike your dwelling, it will be conducted quietly to ground through the framework itself, bypassing you and your precious electronics.

However, if you live in a typical wood-frame house, you might want to consider some protective devices. The most important one for total protection is still Ben Franklin's lightning rod. This should be mounted securely to the highest point of your house (usually the chimney), but well away from any overhanging branches. Large houses may require more than one lightning rod with heavy interconnecting wires mounted well above the roof. This provides a "tent" of protection. A thick solid-copper downlead should be clamped to the rod and held away from the building by insulating standoffs. Avoid any sharp bends in the downlead, which is connected at the bottom to a 10' ground rod of the same type used for grounding your electrical system. If you live in an area where the soil has a high resistivity, you may need multiple ground rods or a chemical treatment to make it more conductive. Your local building code will specify exactly what is needed, and you are well advised to enlist the services of an electrician with experience in lightning protection.

The next level of defense is a whole-house surge protector. Unlike a local surge protector (the kind used with computers), the whole-house device fits into the breaker panel right at the mains. Delta Lightning Arrestors of Big Springs, Texas makes a "300 Series" arrestor with a response time of ten nanoseconds and an ability to clamp 60,000 amps (that's right, sixty thousand). That means, should a lightning surge appear on your electrical line, the arrestor will conduct it to ground right at the box, saving your toys connected downline. DLA products were developed to provide protection for oil-well control gear operating in harsh environments and will sustain repeated attacks, unlike many consumer-grade surge protectors, which are one-shot devices.

If you want to get really, really serious about lightning protection, look into the offerings of PolyPhaser Corporation of Minden, Nevada. PolyPhaser makes protective gear intended for the heavy industrial user; their products are found in transmitting towers, radar installations, satellite uplinks, and the like. They not only promise to protect you from lightning, but from the deleterious effects of Nuclear Electro-Magnetic Pulses (NEMP), a side-effect of nuclear blasts. (The beta-ray emission from a single nuclear bomb detonated high in the atmosphere would produce an EMP sufficient to knock out most communications in North America. During the Cold War, the Pentagon spent millions on this problem, with limited success.) Admittedly, nuclear war might cause you some difficulties more profound than whether your hi-fi is presenting a palpable soundstage. PolyPhaser makes some very interesting stuff, some of it suitable for use in the home. Their catalog is free; in it is an advertisement for an instructional videotape dealing with all aspects of lighting protection.

The final line of defense is at the electrical outlet itself. Most commercial surge protectors will do an adequate job here provided they do not have to dissipate the full fury of a lightning strike. A surge protector is an outlet strip with some combination of MOVs (metal-oxide varistors), inductors, capacitors, clamping diodes, and fuses. An "EMI/RFI Filter" will include some ferrite devices to choke out high-frequency garbage riding on the electrical line. A "constant voltage" isolation transformer forms yet another barrier; in the event of a surge, its core will saturate while its secondary voltage remains steady. A line conditioner may utilize any or all of these approaches; some may improve the sound of your equipment, others may degrade it slightly. Most of those intended for audio use have been reviewed; read the reviews and buy carefully. They are suitable for turntables, video equipment, computers, and all line-level gear—in short, anything which has a relatively constant current draw. Power amps are the exception; their dynamic potential depends on availability of instantaneous current—inductors in series with their power supplies may compromise performance. The best bet here is a couple of MOVs installed across the AC leads where they enter the amp's chassis. Some amps come this way from the factory. Don't attempt a modification if you're not technically competent.

Lightning arrestors and surge protectors aside, some solid homeowner's insurance is your best protection. In fact, as I discovered, there is no substitute for a good insurance policy. What you want, in insurance-industry language, is an "HO2" or "HO3" (broad form or Special form policies); these cover a wide variety of natural, social, and household disasters. Similar policies are available for renters and owners of condominiums. Shop around for the best deal, and be sure the insurance you buy specifies "replacement cost." That way, even if your gear was purchased used, you're covered at full retail.

If you must make a claim, you'll need to back it up with documentation. Remember, normal people don't own $5000 CD players and $10,000 loudspeakers, and your claims adjuster may find it hard to believe that your stereo is worth more than your automobile. Audio magazine's Annual Equipment Guide and the Orion Blue Book are good sources for original retail prices. (Should you be unfortunate enough to suffer a theft, you may need to prove both your actual ownership and the value of your gear.) Make and update an inventory; keep copies of sales receipts and serial numbers. Pictures or video tapes of your equipment should be kept with your valuable papers. In the event of lightning, fire, or other such damage, your insurance company may request written estimates from a reputable repair shop before approving the claim.

When dealing with your insurer, keep your greed in check. Adjusters look askance at inflated claims; if you get too ambitious, you may wind up on the receiving end of a cancellation notice, putting you in the same vulnerable position I was in before this story began.

Charles E Flynn's picture

Laszlo's picture

The Brickwall company makes an excellent and reliable product which does not rely upon sacrificial MOVs. I use it on my stereo gear and on my computer as well.

Charles E Flynn's picture

If I recall correctly, Brickwall and a few other companies license ZeroSurge's patents. It should serve you well. ZeroSurge reports that they have never had a failure.'s picture

Great reprint Barry. In the '89 quake, we were Sony TV dealers. Many, many 27" Trinittrons came crashing down from dressers, cabinets etc. At that time, the major Sony service station was in Santa Clara. Sony fixed the sets for free, back in their profitable days.

IgAK's picture

While it is laudable that the Brickwall brand is guaranteed not to fail, there is this, from their website:

"We believe that surge protectors should not fail. At the heart of our Series Mode Surge Protector is a massive inductor"

This is unfortunate because a series inductor will limit transients of not only the lightning type, but, also the audio type, and will blunt the leading edge rising transient. Inductors are also prone to ringing. Their device also has:

"No surge diversion to ground"

While this seems laudable on the face of it, actually shunting the surge to ground would be done by a parallel circuit such as with the use of TVS (Transient Voltage Suppression) diodes which have super-fast reaction times or GDT's (Gas Discharge Tubes) which are relatively slow to react but can handle huge amounts of current, which will not affect sound quality because they do not limit normal audio transient draw, only coming into use when needed for damaging surges.

Common (and cheap - "get what you pay for") surge suppressors use MOV's which are "medium fast" compared to the two above, about the same or somewhat less capable in current handling than the TVS type but are also parallel shunting types. But they have limited lifetimes that are unpredictable and those green "protected" lights are dangerous eyewash that doesn't go off when the MOV expires, leading you to false confidence in safety that is gone. These must be replaced frequently and regularly but you have no way of knowing when they are dead (or about to be with even one last small transient)...and there's that green light fooling you. MOV's are also considered poor sonically by many as they can distort the AC waveform after they age - another reason to replace them frequently. (See the Zerosurge or Brickwall articles.)

Both the Brickwall and Zerosurge devices are large inductor-based and therefore transient-limiting *all* the time, not just when that is needed for a surge.

A combination of carefully chosen TVS and GDT devices can give super fast picosecond response times and prodigious peak current protection in a non-"sacrificial" package that does not expire under any situation short of a *direct* lightning hit - in which case it may or may not die (depending on lightning hit severity and duration) *after* saving your equipment.

I am not aware of anyone offering such a combination as of yet, so I designed one that has already withstood a lightning hit less than 1,000 feet from my house while all my equipment and computer were on. Not financed for production yet but watch for it. Designed by an audiophile for audiophiles (even includes a nice also shunt-type noise filter)...and, shockingly for audiophile-meant products, is actually inexpensively cheap insurance for your precious gear. Watch for it. Even has a catchy name I can't reveal until that is trademarked.