Lightning striking electric circuits

[Vectronix]

Why does lightning seem to hit objects with free electric currents inside (like computers or cell phones) more than "neutral" objects?

 

[davenn]

Why does lightning seem to hit objects with free electric currents inside (like computers or cell phones) more than "neutral" objects?

computers and other house hold items ... TV's, DVD's freezers etc etc will get damaged because the lightning has hit the outside powerlines on the street
which then conducts the high voltages into the house

a cellphone WONT get struck unless it's plugged into the charger or if a person carrying the phone outside gets struck

 

[anorlunda]

Neutral objects. Do you mean trees? Rocks? Dirt? It does hit them frequently.

I thunk your question is like, "Why does toast always fall butter side down?"

Edit: I forgot the EMP from nearby lightning strikes. Is that what you mean?

 

[Vectronix]

I know lightning hits objects like trees but isn't it more likely to hit something with electric circuits running inside it?

There was an incident where lightning struck through the glass and hit one of the computers here. So I'm wondering about that.

 

[davenn]

but isn't it more likely to hit something with electric circuits running inside it?

NO that is incorrect and will only do so for the reasons I stated

 

[anorlunda]

The thing I forgot in #3 was EMP.

A boat 50 feet away from my boat was hit by lightning. Although I have no direct evidence of a direct hit on my boat, all my electronics (including hand held devices) were fried. The only explanation I could come up with was EMP, but a layman might easily say that the devices were "hit" by lightning.

 

[Vectronix]

Oh okay wow... I didn't know lightning strikes could do that. I'm not very familiar with EMP. Does it propagate as a burst of photons or something else?

 

[anorlunda]

• Lightning electromagnetic pulse (LEMP). The discharge is typically an initial huge current flow, at least mega-amps, followed by a train of pulses of decreasing energy.

In my case, it could have been current coming down the mast, to the thick cable that attaches to a "dynaplate"; an underwater metal plate for grounding purposes. But again, I have no direct evidence, only speculation.

 

[davenn]

Does it propagate as a burst of photons or something else?

just plain old electromagnetic radiation ... Radio Frequency, light

 

[phinds]

Oh okay wow... I didn't know lightning strikes could do that. I'm not very familiar with EMP. Does it propagate as a burst of photons or something else?

EMP means "electromatic pulse". A strong one causes large induced currents in electronics that blows them all to hell and gone.

 

[guigabyte]

I know lightning hits objects like trees but isn't it more likely to hit something with electric circuits running inside it?

Lightning hits power lines very frequently because they are very high, just like trees.

 

[Drakkith]

The thing I forgot in #3 was EMP.

A boat 50 feet away from my boat was hit by lightning. Although I have no direct evidence of a direct hit on my boat, all my electronics (including hand held devices) were fried. The only explanation I could come up with was EMP, but a layman might easily say that the devices were "hit" by lightning.

According to wikipedia, lightning definitely releases an EMP that can disable nearby electronic devices. See here: https://en.wikipedia.org/wiki/Lightning#Transient_currents_during_flash

It makes sense, given that there is a huge current spike within 1-10 microseconds. The ionized plasma channel that conducts the lightning strike should radiate just like an antenna.

Oh okay wow... I didn't know lightning strikes could do that. I'm not very familiar with EMP. Does it propagate as a burst of photons or something else?

All EM radiation is made up of photons. An EMP is a strong burst of EM radiation in the microwave to radio-wave areas of the spectrum. This radiation is absorbed by conductors, just like a radio signal is, and induces are large voltage and current spike in them. This spike can then damage any electronics attached to the conductor (which is often a power line). The EMP itself can probably damage isolated electronic devices not connected to a conductor, but in a much more limited area since these devices don't have nearly the surface area of a large conductor through which to absorb the energy of the radiation.

Just look up the wikipedia article on EMP's for more information.

 

[Baluncore]

So long as we are dependent on sensitive electronics, we will think we are being picked on by lightning.

In my case, it could have been current coming down the mast, to the thick cable that attaches to a "dynaplate"; an underwater metal plate for grounding purposes.

Knowing that must be very comforting, but a significant lightning strike current will not pass through that plate without first blasting away the seal where that plate meets the hull. Changing currents do not flow through conductors, they flow over surfaces, around the outer edge.

External bronze or stainless steel chain-plates are the way to prevent sinking and protect electronics. They keep strikes to the rigging out of the electrical power system and so away from the electronics. It may well be your “common grounding” plate that got your electronics fried.

Lightning sinks small boats by destroying underwater sensors. A sensor's connection cable guides the strike to the surface boundary of the hole in the hull. The wet seal or plastic between sensor and hull may then explode as steam is generated. That removes the sensor and so makes a hole in the hull. It matters little what the hull material is, the insulated sensor cables will provide the guide.

Rigging and external chain plates will normally carry the strike current to remain outside the hull until about 30 cm above the salt water line, where it cuts the corner through the air, away from the hull to spread over, and later into the water surface. An insulated hull without chain plates may have a hole burned or punched in the hull slightly above the waterline. That is where the strike current crosses from conductors inside the hull to the sea surface.

 

[anorlunda]

If you want to spark a lively discussion among boaters, mention anchoring. To stimulate EEs, mention lightning. I'm no exception. I can't resist jumping in with more opinions.

1. I resist anyone making definitive statements about lightning effects or lightning protection. Given 10 repetitions of an experiment with identical circumstances, I expect 10 different results. I have some experience with rocket-triggered lightning experiments so I've seen documented evidence of the variability of current paths.
2. Even among authorities and code-writing bodies, there is no unanimity about lightning protection advice.
3. The "seal" that @Baluncore mentioned on my boat is a 1/2 inch bronze bolt, and the hull is 1 inch thick at that point. Even if the penetration hole was enlarged by a current, it would not leak because the external plate itself forms a waterproof bond with the hull.
4. I heard at least one anecdote about a similar boat with the mast connected to an underwater grounding plate. It was hit, and the the connecting cable vaporized sending molten copper through the cabin; yet the hull remained intact.
5. My boat does have external chain plates, so they could indeed be a current path.
6. There is zero physical evidence of my boat being struck at all. Therefore, one possible scenario is that the EMP originated on the neighboring boat 50 feet away that was struck and damaged.
7. The evidence I do have is two-fold. First: I was on board with 6 other people when hit. I heard a ZAP sound, and thought, "That's very bad." But I recall no flash or thunder. The others on board noticed nothing. If the ZAP came simultaneously with a clap of thunder, I don't think I would have heard it.
8. Second: All the items destroyed (SSB radio with backstay antenna, wind instrument with masthead sensor, radar with external unit halfway up the mast well within the cone of protection, hand held VHF, hand held GPS) were located in the cabin close to each other (within a 1 meter diameter sphere.). The sphere was within 50 cm of one of the chain plates).
9. Other electronics within the sphere were unaffected. VHF radio with masthead antenna. Pactor modem, LED lights. Digital watch. Depth & Speed instruments. GPS chartplotter. Electronic battery charge controller. AC inverter. Hand-held depth sounder.
10. When I visualize an EMP originating on the other boat, the first approximation is an omnidirectional expanding wave. But there are multiple sources of non-uniformity plus reflections on the other boat, on my boat, or from the water surface that could lead to non-uniform concentrations of EMP energy.
11. The only evidence that it was EMP rather than a direct strike is that hand-held devices were affected.

So I repeat. There are so many variables and so many possibilities in an event like a lightning strike on a boat, that it is crazy for anyone to make definitive statements about what did happen or what might happen in the future. When you see a hole blown in the hull (or lightning craze tracks, or vaporized wires), you can safely say that some current went there, but you can't say much about where else the current or the EMP went.

The only word I like to use regarding lightning strike effects is enigmatic.

 

[tech99]

An example of EMP happened to me when I was walking cross London Bridge (London, England) with my umbrella up and lightning struck the next bridge, which was Tower Bridge. A spark jumped from the metal shaft of my umbrella to my hand, a distance of about an inch.

 

[Vectronix]

just plain old electromagnetic radiation ... Radio Frequency, light

Did you think I said 'protons?' =)

 

[davenn]

Did you think I said 'protons?' =)

nope ... why do you ask ?

 

[rootone]

Yep lightning is bad for electronic stuff.
Best to turn off computers and other non essential electronics if it's a serious lightning storm.
Not joking, I have lost valuable stuff twice.

 

[Vectronix]

nope ... why do you ask ?

Well, I said photons and you said no... aren't photons the same as electromagnetic radiation?

 

[phinds]

Well, I said photons and you said no... aren't photons the same as electromagnetic radiation?

You seem to think that photons are like little bullets. That's not what happens. It's an electromagnetic wave. When it HITS something, photons are the result of an interaction

 

[davenn]

Well, I said photons and you said no...

ummm I didn't say no

great response phinds

 

[Nugatory]

aren't photons the same as electromagnetic radiation?

They are not.

A good rule of thumb is that you do not want to be thinking in terms of photons at all unless you're considering quantum mechanical effects, and that's not what we're doing in this thread.

A second rule of thumb is that if you don't like the first rule of thumb you'll have to spend some serious quality time with a graduate-level textbook on quantum electrodynamics.

 

[Baluncore]

I don't think we need to hypothesise an EMP from the lightning strike to the other vessel. Prior to a nearby strike there will be an increase in the local voltage gradient. The UV flash from one strike can trigger local ionisation of the electrically stressed atmosphere, with separate sympathetic parallel strikes to other targets in the vicinity. A local sympathetic strike may not be noticed, but can cause problems for local electronic devices.Now, on the subject of anchors …

 

[Vectronix]

I like the second rule of thumb. I am still learning and I plan on studying quantum electrodynamics.

 

[Dr_Zinj]

Lightning does generate destructive EMP.
We've had several strikes on trees within 50-75 feet of the house that end up inducing a destructive current through the garage door obstruction sensor wires that (1) usually blows out the LED sensors, (2) fries the circuits on the garage door controller, and (3) pops the breaker the garage door opener is plugged into. Never goes past that to have any effect on the rest of the house wiring or electronics. The garage doors were always closed, no external wiring to the system, and no water or other moisture from the outside to the wiring. Only strikes on the 3 trees next to that end of the house generate blow outs; and you can always tell which tree got hit. Mains do not come in on that end of the house, nor is there any other external wiring or metal on that side of the house.

 

[sandy stone]

A good way to tell if your sailboat was struck by lightning is to look at the masthead VHF antenna. If it's still there, you didn't get a direct hit. If it's gone, you did. My boat, which has the mast grounded to the keel, was struck at the dock, vaporizing the antenna and frying the radio, but causing very little damage otherwise. It did appear that a significant amount of current left the boat through the ground conductor on the shore power cable, judging by the burn marks on the plugs.