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lightning inside the house
lightning inside the house
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Old 8th July 2019, 08:19 PM   #81
PRR is offline PRR  United States
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> different Earth rods qualty

The only real thing is length and dampness.

Resistance to distant earth drops significantly as rod goes from 3 feet to 30 feet (1m to 10m). Long rods cost much more to drive, which is why we usually go 8-10' (2-3m), and then drive a second rod 8-10 feet away.

Last summer my sand got very dry. Five rods would not carry enough current to light a lamp. This spring was wet and resistance would be low (good). Because it is all rock a few feet down, I am sure a direct lightning hit would just blast sand and then find another path to follow.

Perhaps the best practical ground in *new* construction is to tie to the metal reinforcement in a concrete foundation. This idea is relatively novel (~~70 years) so not all codes recognize it.

But if lightning is coming down from the sky, a long conducting lamp-hanger will always be an inviting target. I'd switch to lights around the walls. (It's not just the iron chain; even thin-gauge power wires will attract leader-strikes.)
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Old 9th July 2019, 12:08 AM   #82
gabdx is offline gabdx  Canada
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I think it was a direct hit, there was 2 people in the house, I was there at the table , the other was in the living room,

As the electricity contacted, we both lost consciousness for half a second... I felt the first shock..

then the lightning made a steady contact for almost 1 second. During this time, my vision went almost to 0, I lost almost all hearing and only saw some purple things.

Only after it stopped, I regain control, and started to feel pain and shock.

The other person saw me shaking, lights around me going almost 2x intensity, and a very loud current buzzing noise for almost 1 second.

Amazingly, the earth and all the wires redirected the energy to the grounding of the house, and it was not a big strike, just a long, weak one.

The electricity had to jump 2 feet and travel another 2 feet on my skin and the table.

Obviously the grass pan, the wires on the floor, the ON lamps, and the chain, provoked this strike.
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Old 13th July 2019, 05:04 PM   #83
Fast Eddie D is offline Fast Eddie D  United States
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Quote:
Originally Posted by kazap View Post
In the photo see how there are multiple blue purple ground leaders to the left of the main strike. I think this might be what got you. The main strike would go down the wet exterior of your house.


Did your friend see any corona or similar leaders?


Note the absence of any ball lightning in the photo. Rare stuff that ball lightning. With all the CCTV these days its surprisingly rare and seems to be camera shy.



Click the image to open in full size.
I think this explained what happened to me many decades ago.

A bad storm was rolling in fast. I was on my second floor patio trying to get stuff inside the house before it blew away. Lightening hit the utility pole just about 3 feet from the patio and I got slammed real bad. My eyesight was fuzzy and I was deaf for a few hours. I knew it was going to hit but I was paralyzed by the electrical field before it hit. And that is your two second warning - your hair stands on end and your muscles tense up uncontrollably. You can smell it too.

I slept it off and passed a differential equations test the next day.
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Old 15th July 2019, 01:57 AM   #84
TheGimp is offline TheGimp  United States
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I have experienced Ball Lightning when lightning erupted from a power pole at my house (lightning does not strike the pole, it goes from ground to cloud).

I was home one afternoon while my wife was out (198x) to close windows which were left open as a storm was approaching.

When the event occurred, a ball of lightning came out of a switch in the kitchen, passed through to the living room and went out of sight. I lost about $5,000 worth of stereo and lab equipment when it happened.

Ins paid for all of it including replacing several switches and outlets.
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Old 16th July 2019, 03:01 AM   #85
wg_ski is offline wg_ski  United States
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Because the effects of induced fields are not usually as destructive as a direct strike, they can certainly be more “interesting”. In another close call in a rental house I was staying at in grad school, lightning struck outside in the yard close to the utility pole. No damage, but it sounded like somebody hit the telephone with a baseball bat. I’ve never heard one of those old mechanical ringers get that loud before. Just one loud DING, like the anvil hitting the coyote on the head.
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Old 17th July 2019, 03:12 AM   #86
daqvin_carter is offline daqvin_carter  United States
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Actually the rules for grounding a gas pipe are a little confusing.
You are supposed to bond the gas pipe to ground but it should not be considered as a ground.
Is Gas Pipe Grounding Legal? | Electrical Construction & Maintenance (EC&M) Magazine

You should ground the gas pipe but should have a ground wire to the incoming water pipe and one ground stake at the breaker panel.

This is coming from someone who lived in a house for about eight years with no ground at all until I did an addition.
RF interference was a problem until I did the remodel and realized there was no ground to a water pipe or rod at the panel. The house was previously owned by contractors so no surprise there.
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Old 17th July 2019, 05:41 AM   #87
PRR is offline PRR  United States
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> You are supposed to bond the gas pipe to ground but it should not be considered as a ground.

This was already implied in this thread.

#58

All conductors bonded together.

Under current code, one tested dirt-rod or two untested dirt-rods (or alternates as Approved) is your "GROUND".

Note *carefully* the NEC distinction between groundED and groundING.

However gas and water guys are very leery about bonding. When done incorrectly, workers have been killed.
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Old 17th July 2019, 03:41 PM   #88
Tubelab_com is offline Tubelab_com  United States
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I grew up in South Florida which sees more lightning that most of North America (the Gainsville Fl. area is actually #1). I have been zapped by secondary discharges and near strikes several times, and knocked to the ground several feet from where I stood once, which resulted in a blackout incident similar to what you report. I felt funny and seemed stupider than normal for a few days, but all the effects eventually passed.

The knockdown blast was due to a strike on a water tower about 1/4 mile from where I stood. There were about 50 people nearby and several thought I had been directly struck by lightning, but I would not have walked away from such a strike under those conditions. Some even thought that they themselves had been struck by lightning.

This is what actually happened from witness acounts. I had been sailing my 14 foot Hobie Cat sailboat in the Atlantic Ocean off Ft. Lauderdale beach. A storm had brewed up over land and moved toward the ocean. It had started raining, so I got out of the water and put my boat on the trailer. I was completing the tie downs necessary for the ride home when a bolt of lightning directly struck the Ft. Lauderdale water tower about 1/4 mile from where I stood barefoot on the wet sand beach. My hands were in direct contact with the metal boat frame and mast. The mast was stowed horizontally, and only a few feet above the ground.

The earth surface has considerable resistance, and even a well grounded water tower will instantly be at a potential considerably above ground when struck. The closest "good" ground was the salty Atlantic ocean about 100 feet from where I stood. This will cause a voltage gradient on the ground from the water tower to the ocean. The voltage difference between my two feet on the ground could have been quite high at the moment of the strike, causing a momentary muscle spasm launching me several feet backwards.

There will also be a voltage gradient across the air from such a strike causing some current to flow through your body to the wet ground. There is also a very bright visual event and a very loud aural event which adds to the trauma received by the recipient.

This is the reason several people thought that they had been struck by the lightning. It's also why we are told to keep your feet together or stand on one foot, and get as close to the ground as possible if you are ever caught in this situation.

These events caused my body to go through a "reboot cycle" where I went from off for several seconds to a minute depending on different people who were there, to a restart where I began to see, but couldn't move, to WTF just happened, to let me get my stuff together and get out of here before it happens again. This process took about 10 minutes, but I completed tie down and drove home about 10 minutes later.

Most of those videos show a normal arc during a high voltage disconnect event. The loud buzzing sound you heard was likely a phase to phase arc on some high voltage transmission lines. That sound can be very loud, so it could have been at considerable distance. The most likely cause of such an arc is a direct lightning strike on those lines.

An arc on the primary side of the distribution transformers (70 KV to nearly 1 MV) is not usually fused for such a strike, although there are gas discharge devices to dissipate much of the energy. This type of a strike / arc will upset the phase to phase balance for a brief period of time. This is what causes the light dimming or brightening.

Quote:
More realistically 5,000 volts per cm. Maybe even less in humid air.
A lightning strike ionizes the air reducing it's breakdown potential to near zero for a period of time after the initial strike. This is the reason for the secondary discharges. The distribution of the ionized air changes due to the heat produced, and prevailing winds, so the secondary strikes often take a different path.

Quote:
Lightning strikes are high dvdt events
As I used to say gigavolts per microsecond. When lightning strikes, ground is not ground. A high speed discharge into a perfect ground will raise the voltage on the point of strike directly proportional to the distance from the perfect ground, due to inductance. There is also no such thing as a perfect ground. When discharge currents in the 10,000 amp range strike, a ground resistance of 1 ohm will put 10,000 volts on your ground NOT COUNTING the effects of inductance.

Lightning directly struck my neighbors ham radio tower in Florida. He had removed the connectors from his radio equipment and screwed them all to a electrical box which was grounded via a rod driven into the water table in the ground (3 to 5 feet where we lived). His antenna was destroyed, the top two feet were vaporized. The rotator had it's gears welded, but no radio equipment was damaged.

I lived next door, but was not so lucky. My computer was blown, the phones were fried, and my ham radio repeater was reduced to charcoal. WHY?

Remember, ground is NOT ground during a lightning strike.

I had built the ultimate ground for my radio and audio equipment. I had buried an engine block about 5 feet down in the ground. Most of it was sitting in ground water when I filled in the hole. It was connected to a 1/2 inch copper rod at the point where it entered the house with 00 gauge welding cable. The antenna system was grounded to this rod and another length of welding cable went through the wall to my bench ground.

The wireline phone system installed when the house was built was bonded to city water pipe ground on the north side of the house (ground #1). My ultimate ground was on the south side of the house (ground #2). The power company has it's own ground system (ground #3). The strike on my neighbors house put enough voltage between the three grounds to blow the modem board in half inside the PC. Oddly enough the only other item in the PC that got fried was the disk controller board (old 286 PC). I believe the repeater was fried from secondary induced current as well.

It is entirely possible that a lightning strike on some nearby power lines could have caused the situation you experienced. Your metal light support, and the wiring to it acted like the secondary in a transformer that just got a few million volts dumped on it's primary (the power lines or other path for lightning to ground).

If lightning had struck the power system going into your house it should have blown the fuse on the pole transformer, but that doesn't always happen. I have seen sparks fly inside the house I grew up in several times, and once had a spark jump from the aluminum window screen to my nose while looking out the window during a storm (again barefoot on concrete). There was no damage in the house.

These things can be traumatic, and can be mediated, but you can't prevent all of them.
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Old 24th July 2019, 03:36 PM   #89
Fast Eddie D is offline Fast Eddie D  United States
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Quote:
Originally Posted by PRR View Post
> You are supposed to bond the gas pipe to ground but it should not be considered as a ground.

This was already implied in this thread.

#58

All conductors bonded together.

Under current code, one tested dirt-rod or two untested dirt-rods (or alternates as Approved) is your "GROUND".

Note *carefully* the NEC distinction between groundED and groundING.

However gas and water guys are very leery about bonding. When done incorrectly, workers have been killed.
I've seen it done incorrectly more often than correctly. Usually it takes just one visit from the plumber and it's messed up.

I've seen the bonding wire disconnected lots of times. And in my house, a plumber had replaced some steel pipe with copper pipe - and used plastic insulators between the pipes. It's real obvious that this section of pipe bonds the ground wire with the "earth." I had to make the ground wire about 15 feet longer (in conduit) to fix it.

And gas and water guys should be wary. What non-electrical folks don't understand is that the danger starts when you disconnect the pipe. You can bond them together temporarily before disassembly to avoid this hazard. In fact, that's how linemen repair high voltage wires without interruption of service. They use a come along and jumper so they can make a splice without powering down.
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Old 24th July 2019, 04:16 PM   #90
TheGimp is offline TheGimp  United States
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In my area, they run rotating three wire power distribution with ground on top. We have mostly clay soil, with some sand. Soil resistance can vary significantly over a quarter mile range.

Lightning strikes to the ground wire elevates the potential at the strike location causing lightning induced current flow on the ground wire, which inductively couples into the phases below. the top phase gets the greatest coupling.

It is this coupled energy that eventually enters a house causing destruction.

The water line from the meter to the house in my case is plastic.
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