Lightning

[patrick_g]

Statistically speaking, if the conductive tap water were to act as a conductor to electrocute you in the shower then all other plastic plumbed portions of dwellings would also be little electrocution chambers and the insurance statistics would reflect that fact. The insurance companies and various safety organizations keep good records on these sort of things. Those records and statistics do not support the contention that tap water in plastic pipes is a particular hazard.

Several folks have been killed in the USA from being electrocuted while talking on wired phones.

Lightning is an electrical arc. It occurs when the potential difference (voltage) exceeds the ionizing potential required to start the arc. While there is lots to learn yet about lightning, it isn't magic and doesn't have a perverse sense of humor. Damp earth is about as good a conductor as (and sometimes better than) tap water. Lightning shouldn't be attracted to your plastic water pipes much more than to all the dirt around the building. There is a tendency for lightning to hit taller objects (all other things being equal) but a dry attic and dry air space and insulating materials like wood above your head should raise the electrical resistance to a lightning strike at least as much if not more than the slight elevation of your plastic water pipes above the ground tends to decrease it.

If you have metal water pipes that is an entirely different matter. The conductivity of the pipes is so very much greater than tap water that it should make no practical difference whether the pipes were full of water or empty.

A voltage is induced in a conductor (metal water pipe, wire fence, metal roof, or...) whenever it is exposed to a fluctuating magnetic field. A strong fluctuating magnetic field is produced by the current flowing in the lightning strike. So even though lightning may not hit a fence or water pipe it can still induce a voltage in it. This is like a transformer where the lightning is the primary circuit and the water pipe is the secondary of the transformer.

I assert with little fear of well documented contrary information that the likelihood of being electrocuted in the shower is not much more (if any) than standing in the kitchen. If you are the nervous type consider the potential path of the current flow from the water in the toilet up the stream to you.

I'm not scoffing at reasonable precautions and it is not impossible to be hit by lightning in the shower but I think it not particularly more likely than in the kitchen or just being near a water pipe in the floor or wall with all plastic plumbing but all bets are off with metal pipes.

There is an increased lightning risk if you are near a window. This CAN BE substantiated with statistical data. There is an increased risk if you touch metal objects. I wouldn't want to vacuum clean during a lightning storm.

In the olden days (the big rocks were still pretty hot) when I did field service engineering on ships electronic systems (RADAR, SONAR, SSB, VHF, etc.) One of the vessels lost all solid state electronics on board from a close call with lightning. The EMP (ElectroMagnetic Pulse) induces an electric current in all conductors on board and the voltages achieved were sufficient to fry all the chips and transistors on board INCLUDING all the crews digital wrist watches.

No one was injured, no wrists were burned, the crew members weren't hit by lightning but all their watche's solid state guts were fried.

Pat

 

[Oleozz]

My dad built a shower in our basement back in the 60's. I was waiting on the couch until my brother finished his shower (he was older and got to go first) and all of a sudden a huge ball of flame came out of the shower quickly followed by my screaming brother. Lightning had struck, we were to ignorant to realize that you shouldn't be showering during a thunderstorm. I'm sure my dad had told us but my parents weren't home at the time. Fortunately my brother was not hurt but we both learned a lesson that day.

 

[dmccarty]

My dad built a shower in our basement back in the 60's.

Was the water supply metal or non metal?

We contacted our insurance agent and she said the company does not decrease our payments if we have a system to prevent lightning hits. She also said that the research they have said that its unclear if the systems work. I have read this myself over the years so I was very interested in the links in this thread stating that the systems DO make a difference.

The buildings I work in has rods all over it and the company did not install what has to be fairly expensive system for no reason...

When we get bad storms around here its not uncommon to have houses hit and catch fire. I guess the insurance company figures its not real likely to happen. When we built the house I had the insurance company give me quotes on the premium if we had a fire spray system as well as burgler alarms. The "savings" on the premiums where so little that we figured the chance of a fire or theft was pretty low. Our house, roughly twice the size and value as our "city" house costs a bit less to insure...

I guess being rural the chance of robbery or a lawsuit is reduced.

Later,
Dan

 

[Toiyabe]

We contacted our insurance agent and she said the company does not decrease our payments if we have a system to prevent lightning hits. She also said that the research they have said that its unclear if the systems work. I have read this myself over the years so I was very interested in the links in this thread stating that the systems DO make a difference.

The buildings I work in has rods all over it and the company did not install what has to be fairly expensive system for no reason...

There's a lot of confusion about this.

Systems to PREVENT lighning strikes (dissipators, etc.) are very dubious. Many experts think they are snake-oil.

Systems to PROTECT a structure from the effect of a lightning strike (grounded lightning rods) are well regarded, although there's still a lot of disagreement on how to best design them.

 

[horse7]

In the olden days (the big rocks were still pretty hot) when I did field service engineering on ships electronic systems (RADAR, SONAR, SSB, VHF, etc.) One of the vessels lost all solid state electronics on board from a close call with lightning. The EMP (ElectroMagnetic Pulse) induces an electric current in all conductors on board and the voltages achieved were sufficient to fry all the chips and transistors on board INCLUDING all the crews digital wrist watches.

No one was injured, no wrists were burned, the crew members weren't hit by lightning but all their watche's solid state guts were fried.

Pat

A few years ago, a thunder storm cell destroyed the powered GPS external antenna I have on my truck, and damaged an MURS battery powered transmitter. The particular cell that did this didn't seem all that aggressive either, with no particularly violent nearby strikes-- seemed to be more cloud to cloud.

Regularly lightning pops the GFI breakers in the panel box, to the extent that some were removed and local GFI outlets, which don't seem to be as sensitive, were intalled (like, for the refridgerator ). The electronic stuff is on UPSs followed by Tripp Lite isotels (the good stuff is on SmartOnlines).

 

[hitekcountry]

A voltage is induced in a conductor (metal water pipe, wire fence, metal roof, or...) whenever it is exposed to a fluctuating magnetic field. A strong fluctuating magnetic field is produced by the current flowing in the lightning strike. So even though lightning may not hit a fence or water pipe it can still induce a voltage in it. This is like a transformer where the lightning is the primary circuit and the water pipe is the secondary of the transformer.
Pat

Excellent point, any dynamic Electro Magnetic field will induce a voltage/ current surge when it passes through a conductor. And a lightning strike should generate one heck of an EMP. I haven’t given that any thought before, always concentrating on the primary arc, believing that if anything was not hit by the arc it would be ok. Now that you point it out it’s quite obvious.

Thanks for pointing that out.

 

[patrick_g]

Although I have read a bit into lightning, its generation, effects, protection against same, and so forth, I make NO claims about being an expert.

I have seen lots of lightning damage to antennas and associated equipment both as a ham radio enthusiast and a used to be field service engineer on marine electronics (including antennas in high places on ships) Yeah, I took a sabbatical from my typical employ for a couple years and did field service work in marine electronics.

I have seen lots of damage, not all from an actual lightning strike as some of it was from antennas acting as lightning rods and providing a path to conduct the charge away with no actual FLASH BANG.

Lightning rods are there to safely drain away the static charge and prevent lightning from hitting the location so equipped. Their purpose is NOT to take the lightning hits to protect a structure, although that does happen it isn't the preferred effect.

Once upon a time I worked at SUBASE San Diego. Among other things I redesigned the lighting of the Mark 48 torpedo rework facility. Torpedoes (with whatever warhead) have HE (high explosive) components as well as Otto fuel for propulsion. You REALLY DON"T want lightning to hit a place where sailors are handling all this stuff The building complex was surrounded by tall poles with lightning rods on top of them. Each lightning rod gives a protective cone below it of approximately 30 degrees. The more lightning rods the better and higher is better.

Ground wires leading from the rods must be of quite large size and of a good conductor material (big copper conductors.) All bends must be of large radius of curvature to avoid "inductive lumps" and to avoid any relatively sharp convexity. Any convex shape to a conductor concentrates or intensifies the electric field vector and invites arc over.

There is one place where sharp is good. The ends of the lightning rods should be pointed on purpose to increase the local electric field and assist in ionizing the adjacent air to increase the conductivity and prevent additional voltage build up.

When I was in the 9th grade and building and flying model airplanes, one day I was flying one on small diameter multi strand stainless steel cables and a T storm began to approach. The wires began to accumulate a static charge and would arc over the plastic control handle into my hand. Not very painful or damaging but not pleasant. I just hooked my finger over one of the wires to complete the circuit and let the static electricity drain through me and not build up. (Kids always think nothing bad will happen.)

Anyway, the tank in this plane was good sized and it had several minutes left to run but the storm was looming close and eventually even my little pea brain figured out trying to outdo Ben Franklin would NOT be a smart move. I wandered over to some taller grass and brought it in low and fouled the prop in the grass to kill the engine. Better to shatter a prop than to be hit by lightning.

I have also had static electricity drain through my VHF antenna atop my sailboat mast. It was arcing at the connector where the coax attached to the radio. SNAP SNAP SNAP. At first it was slow and not too distinct but it got louder and more frequent. I finally figured out what it was and took a chance. I unscrewed the coax and placed the end away from any grounded metal. There were no cumulus clouds in evidence just some thin to medium overcast gloom. There was no lightning, no storm, and no clear source for the electrical charge. After we arrived at Cat Harbor (Catalilna Harbor) on the west side of the isthmus at Catalina Island, I reattached the coax so as to have VHF two way comms and there were no obvious effects nor was the phenomenon repeated.

Note however that the antenna was a shunt fed 1/2 wave which is supposed to be at DC ground potential and it was connected to an aluminum mast guyed with stainless steel cables which were bonded to a ground system including underwater metal. I won't go into detail but for those who understand the above... yes, there is a BIG contradiction and I didn't and still don't get it.

Static electricity and lightning continue to be studied but remain somewhat mysterious. The closer you examine the phenomenon the more we know we don't know.

Pat

 

[Oleozz]

Was the water supply metal or non metal?
,
Dan

The water supply was metal. (copper pipes).

 

[Toiyabe]

Lightning rods are there to safely drain away the static charge and prevent lightning from hitting the location so equipped. Their purpose is NOT to take the lightning hits to protect a structure, although that does happen it isn't the preferred effect.

Most experts, including Underwriters Laboratories, the National Fire Protection Association and the American Meteorlogical Society, disagree with you. They contend that there is no currently known system that will reduce the chance of a lightning strike. Rounded tips, not sharp tips, are also recommended.

You may find this article from the AMS interesting - Background for the AMS Statement on Lightning Protection Systems

"The fundamental principle in the protection of life and property against lightning is to provide a means by which a lightning discharge can enter or leave the earth without resulting damage or loss. In practice, this is accomplished by providing preferred receptors for nearby strikes then conveying these discharges to Earth and distributing the charges brought down by lightning into the ground so that they do not cause local hazards."

"The early successes with Franklin rods came from sharp-tipped rods exposed on tall structures, as Franklin taught, well above any competing objects. The optimum configuration for the tip of a lightning rod has been studied recently and was addressed in the recent edition of NFPA 780."

 

[patrick_g]

Most experts, including Underwriters Laboratories, the National Fire Protection Association and the American Meteorlogical Society, disagree with you.

"The fundamental principle in the protection of life and property against lightning is to provide a means by which a lightning discharge can enter or leave the earth without resulting damage or loss. In practice, this is accomplished by providing preferred receptors for nearby strikes then conveying these discharges to Earth and distributing the charges brought down by lightning into the ground so that they do not cause local hazards."

"The early successes with Franklin rods came from sharp-tipped rods exposed on tall structures, as Franklin taught, well above any competing objects. The optimum configuration for the tip of a lightning rod has been studied recently and was addressed in the recent edition of NFPA 780."

I'm not sure how they disagree with me. The second paragraph above seems to follow what I think, I think. Further, the first paragraph of the Moore paper you referenced (thanks, it is interesting) relates historical evidence consistent with my view.

Again, I don't claim to be an expert lightning guy, but I do wonder if there is no protection offered by lightning rods why there was an extensive array of lightning rods installed around the Mk 48 torp shop. (Not to mention the comments of the above sited first paragraph of Moore. It could be that once again lots of taxpayers money was wasted but maybe not.

I would be the first to admit that strongly held notions and beliefs get published and taught as theory and or fact and thereby propagate a pool of persons that create inertia which resists change of views when new information comes to light. Galileo was nearly put to death by his pope for claiming NEW information that differed from the currently held (and church approved) cosmological view.

I guess you will have to break it down for me. Could you cite some specific instances where the "powers that be" and I are not in agreement?

I read the Moore thing (skimmed actually) and don't see a thing that I disagree with but I will get back to it for a detailed read (it is interesting) and perhaps find something that differs with my previous understanding.


Pat