OT Lightning does weird stuff...

[skunkworks]

One of our internet services is cable (Charter). We are located in the midwest and lightning storms are very common. We have been down for days waiting for charter to fix the issue. We finally got centurytel to run fiber so we have a redundant connection. Anywhoo - we have had issues with the charter connection taking out some of our network equipment. (we have in line spark gaps and most everything to mitigate this issue). The last resort was putting the cable modem on its own ups and also a ethernet -> fiber converter that hooks into the rest of our network.

Well - we heard the thunder and the charter connection went down. Walk into the area where the cable modem is (the cable modem is sitting on top of the ups and so is the fiber switch). The fiber switch has no lights. I pick it up and see this



cable modem still works..

Go figure.
sam

[MrWhoopee]

Yup, lightning strikes are not common here, but not rare either. I've had two clients lose their DSL modem to a surge coming through the phone line. One also lost the ethernet adapter connected to the modem. I have a whole-house surge suppressor and various ups/surge suppressors on electronics around the house. I still expect loses if there's a nearby strike. After a recent brown-out power event, I lost the control board in our new-used washer, which was not running at the time. Cost almost twice what I paid for the washer. Installed a DPST on the power feed and instructed mama to flip it off whenever she unloaded the washer.

[boslab]

That’s a reasonably high current to melt the case, I can imagine that folk getting zapped whilst on the phone, frightening
mark

[JoeLee]

Something took a hit near by and apparently the lightning came in through a cable and jumped to ground. I'll bet if you look around you'll find other things that it jumped to.

JL...........

[ed_h]

Right out of school, I worked as a design Engineer for a company that made phone line based remote meter reading equipment. Part of the job was to analyze failure returns, and I saw my share of lightning damage. Often, we could actually see the path the lightning energy took inside the unit. More than once we saw vaporized PCB traces right up to a small signal diode, and vaporized traces on the other side of the diode leading to a vaporized transformer. But the diode was still good. Lightning does pretty much what it wants to do.

Ed

[J Tiers]

Right out of school, I worked as a design Engineer for a company that made phone line based remote meter reading equipment. Part of the job was to analyze failure returns, and I saw my share of lightning damage. Often, we could actually see the path the lightning energy took inside the unit. More than once we saw vaporized PCB traces right up to a small signal diode, and vaporized traces on the other side of the diode leading to a vaporized transformer. But the diode was still good. Lightning does pretty much what it wants to do.

Ed

Lightning takes whatever it "sees" as the path of least impedance. Since it is a pretty fast rising wavefront, it acts as a rather high frequency signal, so even things that "look like" good paths may not be for lightning.

The diode does not surprise me. Diodes are tough devices, and are really only "killed" by heat, caused by conducted current. If the pulse is fast enough, it can just go through the diode. The common 1N400X rectifiers were, back when they were developed, rated for 30A or so as a single half cycle *. If that was the rating, they would take more, AND that was an 8ms pulse, fairly long.

Lightning probably would be shorter pulses. Depending on the diode, and trace width, the trace might have a lower thermal mass than the diode, and fail first. The diode might "still work", but might not meet the datasheet spec anymore.


* More recently, those have been dropped by most of the usual makers, and are made by secondary sources. No idea how the specs are on those. I've seen some really lousy performance (Fagor, are your ears burning?) by nominally standard 1N400X parts that the purchasing dept got cheaper. The original makers had specs you could take to the bank.

[RB211]

Well, I think this goes to prove that you should only stick to fiber, lightning will not travel on fiber. I would even go as far as using fiber to connect multiple buildings together to mitigate the issue. You can use media converters to go from Ethernet - Fiber - Ethernet.
It sucks that the lightning came in on the Coax connection then jumped to only kill the fiber!
You should see what it does to airplanes. Commonly destroys radar domes, blows out structural rivets, and the exit location is usually covered in tiny pin holes. If you ever see a brand new 777 and notice it has metal patches rivetted in random spots along the fuselage, now you know why!

[J Tiers]

Well, I think this goes to prove that you should only stick to fiber, lightning will not travel on fiber. I would even go as far as using fiber to connect multiple buildings together to mitigate the issue. You can use media converters to go from Ethernet - Fiber - Ethernet.
It sucks that the lightning came in on the Coax connection then jumped to only kill the fiber!
You should see what it does to airplanes. Commonly destroys radar domes, blows out structural rivets, and the exit location is usually covered in tiny pin holes. If you ever see a brand new 777 and notice it has metal patches rivetted in random spots along the fuselage, now you know why!

Back at the music company, we had 2 buildings about 150 feet apart across the parking lot. They were connected by copper connections, with opto isolators (a data rated commercial isolator unit).

The connection was reliably dead for at least some users after a thunderstorm until the connection was replaced by fiber. One or more channels would be kaput, and have to be replaced.

[Mcostello]

Guy at work was looking out of His picture window watching a lightening storm. A lightining bolt hit the ground 4' away from the front of the window. Hit His waterline and blew it in two. Water spout in the yard. He could not see temporarly, Wife was screaming, electric sparks jumped out from all His outlets, the outlets by the windows caught some curtains on fire. When He could see He helped put out the fires. Whole house got rewired. You would think the lightining would have preferred the nice juicy ground in the ground.

[J Tiers]

[QUOTE=Mcostello;n2001553]Guy at work was looking out of His picture window watching a lightening storm. A lightining bolt hit the ground 4' away from the front of the window. Hit His waterline and blew it in two. Water spout in the yard. He could not see temporarly, Wife was screaming, electric sparks jumped out from all His outlets, the outlets by the windows caught some curtains on fire. When He could see He helped put out the fires. Whole house got rewired. You would think the lightining would have preferred the nice juicy ground in the ground.[/QUOTE]

It apparently did.... since it penetrated to the water pipe.

The other damage was probably by induction..... The very high current of the lightning stroke would have induced currents/voltages in any other nearby conductors. Those induced currents/voltages would explain the sparks and resulting fires.

You have an air-core transformer, with the ionized path of the stroke as the primary, and whatever wires are nearby as the secondary. High frequencies are fine with that, you see such coils in older radios. You can get quite a bit of power through such a "coil pair", if they are fairly close together. If farther away, the effectiveness of the coupling is less, induced voltages etc are less, and may be non-damaging.

[PStechPaul]

Probably more than 25 years ago I was on a flight destined for Sea-Tac, and there were heavy storms predicted for the area. At one point there was a bright flash and loud BANG, and the lights in the plane flickered. The college age girl sitting next to me grabbed me ( I was OK with that ), and was very rattled. She said she was a pilot for her father's small plane, but had never experienced anything like that. The pilot came on the speakers after a minute or so and announced that it was only a "static discharge" and nothing to worry about, but I think that was just a euphemism for lightning strike. I think the landing was normal.

[I make chips]

It certainly does odd things. A guy I know had his garage hit by it. Zero damage to the garage other than a burned spot on an aluminum window frame. His car was in the garage. The plastic inner fender was blasted to bits with pieces all over. No other damage to the car or anything else.

My house got hit ~20 years ago. Same burned spot on a window frame and it took out the controls on the dish washer. A few weeks later the well pump died.

[Black Forest]

I had a lightening strike hit one of our outside water troughs for our horses. It killed three horses that were about 6 feet away. This was in Florida back in the 70's.

[Ringo]

I'm retired aircraft mech. Many years on King-Airs and the military variants. Many lightning strike inspections.
Why does lightning always pick out the left prop? it would jump out (or in?) of a single blade on the left engine.
Why always the left?
then a single row of rivets down the fuselage, all looked like you struck a match head on each rivet.
and it blew the cap off the top of the rudder. but, no burn marks between rudder cap and fuselage (vertical stab)
All the electrical/avionics worked fine post landing, but, avionics failed on subsequent flights, one at a time, until you replaced everything

[darryl]

We don't often get lightning storms here anymore, but last time we had one I stood outside while it flashed within about 1/4 mile on both sides of the house. What a show! I was waiting for that tingling feeling that would mean RUN FOR COVER, but it didn't happen.

Reminds me of the time I was in Africa, living in the highlands district near Salisbury. We had a period of about two weeks where lightning would strike the pole in front of our house several times a day during the afternoon. You'd see the flash, then a fraction of a second later you'd hear the bang. Sometimes I'd stand in the yard and watch it. And of course, being a geek I'd wonder how to capture the energy. It's been said that one lightning strike has enough energy to run a household for a month or more- this would have ensured power all year long, assuming you could capture, store, and use the energy in some efficient manner.

Our home insurance included a glass breakage clause, as it was common in our area for thunder to break windows.