additions... 02

...the real world...

what's lightning..?

Such a question recuire a rather complex answer. Not sure you'd like that, so, ok... the short variant follows...

Lightning is a whole array of events that are all caused by discharging high voltage, high energy, electrical fields over an isolating gap. The spark-plug in a car-engine is a simple man-made variant. Nature's variants are a bit more...

What we get to see is a spark bridging the gap between a highly charged cloud and earth, or between two differently charged clouds. It is all about charges and discharges, and we only get to see the discharges.

What we rarely get to see because it's all happening so fast, is that lightning usually is at least a two-phase process. One small spark from earth towards the cloud, followed by the real, flashing, spark from the cloud towards earth.

The blinding lightning-flash we get to see is following the path prepared by the tiny leading spark, as the air has become a slightly better conductor along that path. So you see; lightning isn't flashing randomly towards earth. Lightning is always preparing its own conductor first by ionizing the air, and then throwing everything it has at its disposal onto this conductor — in a flash.

This huge flash or spark may spread quite a lot away from the leading path, as the forces are seeking the best conductivity on their way. There may have been a lot of small, invisible, leading sparks that didn't trigger the big one, and air is not a stable mass. Lots of variables here that are resolved in a flash — even without computer-calculations. Nature knows its own ways, and use brute force.

The charging / discharging can go in all directions, as all elements that are isolated from each other can become negatively or positively charged in relation to each other, caused by wandering electrons. Separation and isolation are primary factors, as contact between charged elements results in they both being discharged and ballanced in relation to each other. It is all relative, so you need at least two, separated, elements in order to have charges and following discharges.

There may be lots of separate elements in a cloud build-up, thus many charge-relations. As cloud-formations move, all these charge-relations will interact, and there may be some peaceful exchanges of electrical charges and some more violent and visible ones. The process is so complex and dynamic that there's no way to calculate it other than in very rough terms.

Visualizing this process down to the level of separate electrons is a lot easier — once you've got the hang of it. Let's not go down that route now, but let us instead enjoy the magnificent demonstration of these natural forces on display. We get the whole show for free, as long as we stay out of harms way.

What we should understand is that charges will pull on each other even over great distances, and once the difference in charges gets high enough, and the energy is there, they will prepare discharging-paths and bridge the gap. Whatever gets in the way will have to take part in the exchange – whether it can take it or not– so better try not to get exposed to it.

awesome power…

You don't think we can hold back the awesome power from a lightning-strike? Guess not… if it hits too close. Half a million Amperes released during a few microseconds is a quite small "show of force" from mother nature. She can do a lot better than that in a blink of an eye.

Well, there's the key to it. As long as there are at least a few hundred meters/yards gap between our equipment and the lightning, then we definitely can do something about these forceful but short bursts of electricity. Let's try to keep the lightning from bridging that gap with full force. Let's disperse and dampen it a little before it reaches our precious equipment.

Lightning always follows the best conductors awailable, and if one or more of those happens to lead through our equipment — "goodnight". There may just be enough damage to make a computer highly unreliable, or the poor thing may simply stop working because there isn't much left inside. Accessories are often even less capable of handling lightning-bursts, so we may have widespread damage on our hands.

However, if we make the conductors towards and surrounding our equipment a little less attractive for a lightning-discharge, and add in some really attractive discharging-routes, we may improve our chances a lot. Mother nature can be persuaded to discharge her powers elsewhere if we ask — nicely.

This is tricky stuff, because our electric power supply systems and various regulations surrounding them are not always taking the laws of nature into account. There's a lot of theories and "wishful thinking" around these things. We may have to work on the edges in order to make them all meet on common ground.

I can't cover all the different systems and regulations for main electrical wiring in countries around the world. I have to leave it to each individual to sort out their own systems and regulations. Read everything on this page as basic information which apply wherever and whenever lightning strikes around our globe, and the effect it may have on electronic equipment connected to ordinary single-phase systems as used in homes and offices.

dampen and discharge…

I'd like to isolate my electronic equipment from the outside world, since that's the best protection there is. However, I need some contact so the useful parts can get through, as it is pretty difficult to make electronic equipment work without power. I'd like to set some strict limits though.

I have some old components left over from my days in the electronic industry. They are small and blue, and they can make most modern dischargers blue in the face with a little help. Well, I think you can get them in any colors, but that's not the point here.

These small components are called "varistors" (short for: variable resistor), and they will change their resistance from infinite to zero depending on what voltage we expose them too. Once above the treshold-voltage they will start to conduct better and better quite rapidly. Nice feature, as they can discharge high voltage bursts while leaving the normal voltage untouched.

Now, varistors cannot take much power for any length of time—5Watt or so, but they can carry enormous amounts of power for very short time-spans. 15,000Amperes for 8μseconds is typical. That's enough to discharge a fairly strong power-burst from a lightning-strike near by as long as we provide some dampening.

Now, if we can make the conductors—power lines—leading towards our equipment a little less conductive by adding some resistance to them. That'll make them less interesting for a lightning-burst, so it will discharge more of its power elsewhere end leave less for the varistors to handle, but normal supply-voltage must not be affected.

A few modest "coils" of insulated copper-wire wound up on some plastic-tube, cross-connected by some discharging varistors, may well save our equipment from ever having to feel the power of mother nature's fireworks. Coils are conducting well for low frequencies—50/60Hz — that's our mains. However, coils don't conduct particularly well for high frequencies, and power-bursts from lightning-strikes are definitely high frequency, so coils are high-resistance conductors seen from a lightning-strike's point of view. High resistance means "lousy connector", so power-bursts will be dampened.

Does the above sound like a joke? Well, you may find these varistors and these coils inside some of the best and most well-protected electronic equipment made today. That's because this "joke" actually works.

let's scale it up…

We can make such protections on a slightly larger scale, and put them before all our equipment. Done well it may provide maybe 100 times better protection than each of those well-protected devices have built-in. That's not too much.

Spacing things a little bit apart is a good thing, as lightning-bursts can jump. A few centimeters, or an inch or two, between each part may prevent that, so let's not miniaturize our protective device.

3 - 4 coils of ordinary, insulated, wiring connected in series on each phase of a 2-phase supply-line. That'll give us 6 to 8 coils. Each coil may consist of 2 meters/6 feet of cable wound nicely and tight in one layer around a piece of 12cm/½inch plastic tube. Plastic water-pipes are fine as cores. The end-result is a bunch of air-coils.

Basically, these coils shall not represent any resistance for 50/60Hz cycles on our mains, so some testing and measuring should be done before they are fixed in place. All coils in series should not cause any voltage-loss when fully loaded, and no heat should be generated from them.

These coils can be fine-tuned for optimal functionality almost independent of exact core-size, frequency and wire-dimension. My way of doing this without actually calculating the precise reactivity may seem a little strange and un-scientific, but I often use similar methods on calculated components also because it works so well. Patience is important at this stage, and remember: full load. No varistors should be connected during this fine-tuning process.

These coils are correctly tuned when they become 5-8°C warmer than a similar fully stretched out wire and the loss is about 2-3Volts fully loaded. If they get any warmer and/or the loss greater, then they have too many turns. If no heat and loss, then they have too few turns.

The closer to the edge these coils are tuned, the better protection they provides. A little back and forth, and giving them some time to heat up and cool down, and they are right on the edge.

Varistors are connected between the 2 main phases at each connecting-point between those coils see fig 2. That'll give us 2 series of coils with 4 varistors as cross-connectors. Varistors can work in parallel, so more can be added for extra discharge-capacity. However, no two varistors are identical, so you can't add them up in a calculation.

Parallel varistors will act as back-up for each other, so that when one starts to fail the parallel one with slightly higher treshold will start working harder. A varistor's treshold isn't all that sharp, so all parallel varistors will discharge some current during a lightning-burst, but not in equal amounts.

By building such a protection as a separate, incapsulated, unit, and plugging it in between our main supply and our equipment, we end up with a freestanding protection-units that can take quite a punch. It can't stop direct hits, but then again: nothing can.

Such protections must conform to regulations in each country. It is definitely not a "do it yourself" job. Use ordinary materials for main electrical supply, and make sure all live connections are safely covered so they can't be touched by humans and/or animals.

why not use fuses…

By all means, add fuses to the chain. However, even the fastest fuses are generally too slow, so they can't replace those ugly and large coils for protection against lightning-bursts. Put fuses in front of – before – the protection-chain.

Ordinary fuses must heat up and burn off, and that process takes much too long to be of much use when lightning strikes. Fuses may however cut off supply later during the discharge-phase, and help minimize the work-load on the varistors. Thus fuses are a good addition.

Automatic fuses? Well they are even slower, but they might do some good when connected correctly in front of the protection-chain. Automatic fuses are highly unpredictable when exposed to lightning-burst.

it won't last forever…

Such protections must be inspected after lightning-strikes – once it is safe – and the varistors exchanged with new ones if there's the slightest chance that they have been overloaded. Not much use in overloaded or burned-out varistors I'm afraid. Protection against the mighty forces of nature must include a weak link.

Varistors can be blown completely to dust by some extra nasty and close lightning-burst, but they have probably done their job before they go. Then they'll just leave it to the next varistor down the chain to take the next blow, or they short-circuit and blow the main fuses. Each set of coils adds some extra dampening, but there may still be some enormous amounts of energy left to discharge.

Just think about it: these tiny varistors may have to discharge several million times more power than they can sustain continuously. No wonder they'll be worn down and become less reliable after a few of those. Better put in some fresh ones while you have the chance, and fasten them well. Varistors cost a lot less than a computer or accessory.

components and cost…

Varistors: for 220 - 240 Volt mains, use 380Volts varistors — 15,000Ampere/8μS (or better).
For 110 Volt mains, use 150Volts varistors — otherwise same data as above.

Cables: use normal type and size used for wiring in your own home, and pay attention to the size/Ampere your main fuzes have leading to where such protection should be used. Don't use thicker cables than they have to be, but not thinner than legal size for mains in your own country.

Cover / box: use any legal type for electrical wiring. Make sure it's a "non-conductive" one—no metal-boxes here. Get a large enough box with a lid that makes the wiring inside accessible for inspection.

Cost: don't know, but I paid something around 50¢ a piece for a few varistors a few years back. Electrical cables are identical to those used for normal wiring in any home, and should cost the same as those.

no ground..?

What about the electrical ground? Well there isn't any in my examples. If you wanna add protection by discharging lightning-bursts to ground, then do it at, or close to, the main power-intake for your building. Anything else will be too weak.

Use ready-made over-voltage protections—a lightning arrester—that'll clamp down and discharge to ground on your power-intake, and get a professional electrician to do the job for you.

Mains wiring differs from country to country around the world. This type of wiring is quite common: "live" - "neutral" - "ground", and I'm only using "live" and "neutral". Electricity behaves the same everywhere, but rules and regulations do not.

I'll get it wrong for some country no matter how I explain it, so I won't go in depth here. If you don't know what you're doing with regard to the rules and regulations in your own country, then leave it to the professionals.

Any amateur-jobs on electric wiring at your end will probably do more harm than good. You may even get yourself killed, which is not recommended whether you're a web designer or something completely different.

Ground mains somewhere else…

Your equipment will not be protected from lightning-strikes by connecting it to earth or ground, and only a few of the larger items you have may be provided with a proper ground anyway. Lightning-bursts are more likely to use a ground-wire to enter or leave your equipment through, so you're most often better of by not connecting any of your equipment to ground.

Some "experts" may disagree quite loudly, but they don't know much about lightning. I've worked on the effects of lightning on all kinds of electrical equipment, and lightning-bursts follow the laws of nature. Lightnings are just a bit too massive to be calculated with any degree of precision — that's all.

For a few μsecond or so all ballance in all electrical wiring is lost. Only the most extreme grounding-measures can prevent that, and we don't build that kind of grounding into our homes and offices. The extra grounding-wire in electrical cables is just another un-ballanced conductor that we might as well do without.

Good grounding elsewhere may help protect your electronic equipment, by letting some of the energy discharge — elsewhere. That's the whole idea—discharge lightning-bursts somewhere where it does less harm.

Interconnecting electronic equipment with a quite solid ground-wire is a good thing though. That'll keep them on the same level, and ground/screen in their signal-cables won't have to carry the load. See further down.

lightning-rods…

Lightning-rods, with their massive direct connections to earth, may provide lightning with excellent discharging-routes. They are good examples of "grounding elsewhere", and may keep the entire discharge away from our buildings and electrical wiring.

Some lightning-rods are really good constructions which seems to create leading-sparks and attract lightning. Other lightning-rods are just (hopefully) "standing in the way" when lightning strikes near enough. Most lightning-rods are providing some protection.

There are still a lot of unknown variables concerning lightning-rods. We know that some constructions and positions may work better than others, but since it's a bit difficult to measure what's really happening in the short moments before and during a discharge, more theories than actual facts are still surrounding these issues.

confined environment…

By keeping all your electronic equipment relatively close together, you may provide protection for it as one package. If you position parts of your equipment in different rooms, connect it to different power-supply-lines and interconnect these units by signal-cables, then lightning-bursts may simply "rip it apart".

A power-burst from lightning spread according to its own rules, and those rules are highly unpredictable. For a few microsecond there may be several hundred, if not thousands, of volts difference between two units supplied from different parts of the mains in the same building. Such "rip-offs" may easily be too much to take for some tiny chips inside your units.

Wireless data-connections between such separate units are one simple way to protect against such "rip-offs". Optical connections is another.

The safest is to keep all inter-connected equipment connected to the same power-source and sharing the same protection. Then the whole "package" will be thrown in the same direction by any lightning-burst, and no "rip-offs" can occur.

more rip-offs…

"Rip-offs" of another nature are often causing unexplained failures in electronic equipment. Static charges may cause a lot of damage to electronic circuits, and the smaller and more compact microchips and other components becomes, the less they can take.

Static charges can build up in most non-conductive materials, and dry air is an excellent insulator. Thus low-energy charges can build themselves up to thousands of volts in pieces of carpet or whatever. We may not notice these charges, and we may even be charged ourself without knowing it.

Static charges can discharge through any conducting or semi-conducting item. Microchips are easily destroied by such uncontrolled discharges simply because their internal conductors have become so extremely thin and the insulating layers between them equally thin.

Interconnecting electronic units by solid ground-wire and keeping relative humidity in the environment at close to or above 70%, will prevent high-voltage charges from building up. No static build-up means that no destructive discharges will take place.

Preventing static charges from building up will also help when those much larger charges from lightning comes our way. Stray charges caused by lightning will then also be kept small, and they will discharge in a much more controlled way.

external communications…

Phonelines may be a weak point when lightning strikes — if they are copper-wire. If you have optical cables for all your digital communication-lines, then you can just forget about it.

Copper-wire communication-lines are often used locally, even if the main core is optical. Lightning see copper-wire phonelines as excellent conductors, and will follow them and discharge through your modem and/or switch-box. Some protection may be needed here, and it's a lot simpler than dealing with our main power supply-lines.

It's of little use to dampen and discharge high-voltage bursts on a phoneline only onto the line itself. Lightning-bursts will get through and discharge through the connected equipment, modem or whatever, on its search for earth. It will discharge towards the main supply-lines, so let's give it a more direct route.

The way to do it is to provide a discharge-route to the same mains as our equipment is connected to, and dampen and limit the charge itself. No need for coils here, as a few cheap resistors and three varistors will do an excellent job.

One 10Ω/¼Watt resistor is connected in series with each copper-wire. These resistors will act as dampeners and fuses, and will most often blow when lightning strikes. Add fuses too if you like, but don't skip these resistors. Fuses are too slow to act as dampeners, as mentioned above.

After these resistors a varistor is connected between the two copper-wires. A 15,000Ampere/8μsecond/120Volts are best here. Phonelines are normally carrying 40-50VoltDC, falling to around 6VoltDC when busy. This may vary slightly across the globe.

From each leg of the varistor above, we'll add in two more. Each of these should have a value of 15,000Ampere/8μsecond/380Volts, and have its other leg connected to one wire on our main power supply-lines. Thus we are discharging high voltage bursts on our phonelines to our mains See fig 3. Remember that our mains need a protection of its own like the one in fig 2 for the whole thing to work safely, and the phoneline protection must be connected to the mains after mains own protection.

After these discharging-varistors we add one 22Ω/¼Watt resistor to each wire. These will add protection during the discharge-phase by dampening the rest of the burst to a level that a modem and/or a switch can handle on its own.

Protect it well and make it like an adaptor by providing it with plugs and connectors for both phoneline in/out and main power supply-line. Also, make it easy to access for inspection and exchange of those resistors — they will blow. On the other hand, resistors of that size should cost less than a cent each, so there will only be the small job of replacing them once it's safe to do so.

Finally…

Ok, a short FAQ at the end. "I" am the author of this page.

1. Do I use these protections myself?
   - Yes, I do.
2. Do they work?
   - Yes.
3. Do I leave everything on during lightning-storms?
   - No, I pull the plug as quickly as I can, and take cover.
4. Are there other protection-techniques?
   - Yes, plenty, but most which works are variations on the above.
5. Can lightning-protections be bought in shops?
   - Yes, but most lightning-protections sold in shops are not worth much.
6. Would I recommend others to create such protections themselves?
   - Definitely not! This is for professionals who know what they are doing.
7. Do I know what I'm writing about?
   - Sure, I've dealt with these issues professionally for years.
8. Why can't I be more specific?
   - Because we are dealing with natural forces that are not quite well understood even by professionals yet.

That's the realistic bottom-line on the issue of lightning-protection.

sincerely 

Hageland 09.apr.2004
last rev: 04.apr.2006