A Bolt from the Blue: Lightning strikes vs. Home electronics

Home | Audio Magazine | Stereo Review magazine | Good Sound | Troubleshooting



One evening late last summer [article account written in early 1994] I took the most expensive workout of my life. In my hurry to meet a friend at the gym, I left the house, leaving my computer and hi-fi on despite the ominous look of the sky. In the American South, experience teaches you to dash about disconnecting everything at the first sign of a thunderstorm. Usually I do, but this time my mind was elsewhere.

I headed across town toward my favorite gym. Stopped at a hilltop intersection, I saw one of the new office towers take the biggest lightning strike I have ever seen. The building, 40-some stories of Gothic Modern topped by a decorative open-ironwork chisel point, lit up for a few seconds like a gigantic searchlight. Then came the deluge. For a quarter-hour rain fell like Niagara Falls, visibility shrank to about 20’ and traffic slowed to a crawl.

During a lull I parked and dashed into the gym. It wasn’t very busy--just me and five or six other lunatics. I trained for about an hour while the thunder boomed and rolled. My friend never showed up. He missed a great experience; there’s a primeval charm to pumping iron while Nature rages. Outside, it looked like Zeus was pressure-washing the city with a galactic fire hose. Inside, the lights dimmed and brightened, went out and came back on. Power failures are common in this part of the world: trees fall across electrical lines, cars slam into utility poles, lightning strikes everywhere. It’s like earthquakes in California; you accept their inevitability and assume that you’ll be lucky. This particular evening my luck ran out.

When I came home I found Jannie standing in the dining room. She was looking at hundreds of pieces of plaster scattered over the table and carpet. The house had taken a direct hit! The innermost wall had a shotgun-blast hole near the ceiling, which in turn had a smaller hole by the outer wall. (Entrance and exit wounds? I wondered.) We began a cursory examination of the damage.

The phones were dead. The bedroom TV worked but the cable was out. Sound but no picture on the big Sony. Two VCRs were inoperative. My software was still displayed on the monitor, but the computer wouldn’t respond to the keyboard. A rack’s worth of audio gear was kaput. In the kitchen, a small TV was dead, but the KLH model 21 table radio plugged into the same outlet worked fine. So did the kitchen appliances, including the microwave oven. Curiously, there was no correlation between surge damage and whether or not anything was actually powered up at the time of the strike We walked around testing and unplugging things, as if that might prevent further destruction. The storm continued all night.

The next day I began some inanimate-object triage. The damaged were divided into three groups—the irreparable, the easily repaired, and those that with great effort might be brought back to life. There were some pleasant surprises: among the survivors were a Pioneer CLD-2080 laserdisc player, a PS Audio 200 CX power amplifier, and a Randy Tomlinson-modified JVC XL-Z1010 disc player. Light casualties included a Panasonic portable phone (new AC adaptor) and an Adcom GFP-565 whose tape-out buffer chips were blown even though its phono and line stages worked normally. My old reliable answering machine was beyond hope; its printed circuit board was charred. A cheap telephone attached to it had suffered permanent brain damage; it would receive calls but dialed wrong numbers. It was trash- can time for the two of them. The phone line which fed them was burned open.

A stack of line-level gear (tape decks, tuner, cheapo carousel changer, etc.) had been plugged into a “surge-suppressor” outlet strip which was in turn plugged into an isolation transformer. The strip didn’t get a chance to do much suppressing; the isolation transformer suffered an open primary. This was actually fortuitous for everything it supplied—they all came through unscathed. Worst hit were the NEC video recorders in another room, which, being connected directly to cable and AC outlets, were doubly susceptible. One had some shorted power-supply components; the other was so fir gone I decided to strip it for parts.

Fixing the computer was a comic nightmare. I have an IBM XT with a monochrome monitor and some outdated software, which works just fine for what I do with it. If that sounds a bit defensive, it’s because I know a certain percentage of readers are technoholics, which is fine; it’s just that my testosterone level and self—esteem are not directly related to the size of my on-board memory or the speed of my microprocessor. Occasionally I write up an invoice or mull over a piece for the magazine, and I’ve found every time that, even at my best, I can’t out-type the old IBM. Most of the time spent writing, which is a rare enough occurrence (sorry, JA), is time spent staring out the window or changing “glad” to “happy.” In other words, I need a 486/50MHz with glittering, variegated fish swimming across its high-resolution screen like I need a third leg. My fondness for the XT stems from my days as a computer tech, when Big Blue was ship ping this machine by the millions, it was standard equipment in every respectable office, and le derriere du chat for the home computer jock. It’s big and accessible and easy to work on and parts will be available forever. Or so I thought.

If you think the audio world is badly infected with the latest-and-greatest syndrome, you haven’t been paying attention to computers. Or maybe the fact that newer and better DACs seem to be unveiled every month has made you aware of rapid developments in the digital realm. My particular sad truth is: the XT is several generations out of date. I called around to computer stores to find parts. Sample responses: “We don’t service those anymore.” Click. “Why do you want to fix that old hunk of junk? It’s a dinosaur!” Click. “Sure, we can get you an original IBM motherboard, $250 I think.” Click. “Why try fix? XT obsolete. Need 386. Come in, we make deal.” After three days of this, I heard about a computer salvage shop, literally an electronics junk yard, in a disreputable part of town. There I found every thing I needed, at prices so low I had to stock up just in case: motherboards $17, keyboards $20, printer ribbons two for a dollar. I was up and running again.

So, what does this have to do with audio? Big repair costs, that’s what. How much? Let’s ignore my resourcefulness and add up the tab as if this had happened to a typical retail customer:

Beyond Repair: Replacement Cost

1 NEC hi-fi stereo VCR $465

1 answering machine $90

1 telephone $40

1 isolation transformer $60

1 AC adaptor for phone $28

Repaired: Parts + Labor

1 Adcom preamp $125

1 Sony Profeel monitor $200

1 NEC hi-fi stereo VCR $150

1 computer $250

1 13” TV $85

Total: $1493

The phone line was repaired by the phone company (maintenance fee: $24/year), and the TV cable at the utility pole, two weeks later, by the cable company at no charge. “That storm’s given me 50 hours of overtime so far” the repair man grinned.

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 sales men. 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 Indus tries 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 your self 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 LPL)

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 cha within the cloud, positive above and 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 thou sands of feet of air between it and 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 storm clouds.) 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 thou sands 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 pip- squeaks compared to Mother Nature. A lightning flash may consist of several strokes, each about 50jis 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 mid west 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: north eastern 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 aver age 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 every thing from wall outlets, cable feeds, and telephone lines. Out let 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 con tents? First you need to assess your likelihood of 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 frame work itself, bypassing 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 down- lead, 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, as are 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 often nanoseconds and an ability to clamp 60,000 amps (that’s tight, 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 in tended 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, any thing 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 theft 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 to the contrary, 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 “H02” or “H03” (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 owner ship 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.

MORE INFO:

SOURCES FOR LIGHTNING PROTECTION HARDWARE

  1. Delta Lightning Arrestors, Inc
  2. PolyPhaser Corp
  3. Cushcraft Corporation

INFORMATION/WEB

  1. Insurance Information Institute
  2. Edison Electric Institute.
  3. Lightning Protection Institute
  4. Underwriters Laboratory
  5. National Fire Protection Association

BOOKS

  1. All About Lightning, Martin A. Uman, Dover Publications, 31 East 2nd St., Mineola, NY 11501, ISBN 0.-486-25237-X.
  2. Lightning, Martin A. Uman, Dover Publications, ISBN 0-486-64575-4.
  3. The Lightning Discharge, Martin A. Uman, National Geophysics Series Vol.39. Academic Press, Inc., division of Harcourt Brace Jovanovich, ISBN 0-12-708350-2.
  4. (Uman is a professor of electrical engineering at the University of Florida, Gainesville.)
  5. Violent Storms. Jon Erickson, TAB Books, Blue Ridge Summit, PA 17294-0214, ISBN 0-8306-9042-5.

.

 


Prev. | Next

Top of Page   All Related Articles    Home

Updated: Thursday, 2017-07-06 18:57 PST