Will T.V. "attract" lightning

[frankiee]

When I was young I was led to believe that during a lightning storm that we turned off the T.V. because when left on it could attract lightening.
I still turn it off during a storm but usually don't unplug it.
What is the story on T.V. during a storm? Can it blow up?
Will shuting it off help?
I take it for granted that the cable is grounded somewhere.
Thanks

 

[rbulsara]

TV itself may not attract lightning, but if you have an outdoor antenna conncected to it, that will attract the lightning.

Regardless it is advisable to turn the TV (and like devices) off during a storm as lighting, even strck a few miles away, could induce voltage spikes in the electrical distribution system that eventually could find way in the TV or any other applicace connecte to a plug. TV or like electronic devices being more sensitive to such voltage transients, it is a good practice to turn them off.

For news rely on a battery powered radio or mini-tv (battery powered) during an electrical storm.

( by the way I have none of those battery powered devices, but can advise nonetheless)

 

[itsmoked]

frankiee; lightning will explode just about anything if it suffers a direct hit. Trees explode because the sap vaporizes. Certainly a TV could explode, probably would if struck directly. That said... The chances of your tv being directly struck are probably only marginally greater than you being struck! More likey is that a nearby strike might occur, depending on your locality, that could "induce" voltages inside your tv that could damage it. Also a strike could hit your power lines, (probably need to be within a mile), and this could "conduct" a high voltage into your tv also possibly damaging it. But explode? Do not worry about it. Your tv will never explode.

If you are concerned about lightning/tv problems then do not turn off your devices, UNPLUG your devices! Large induced or conducted voltages can easily jump any tv power switches and indeed few tv's have power switches anymore, they really have wakeup and goto sleep switches.

On another note: DO NOT TALK ON HARD WIRED PHONES DURING THUNDERSTORMS as several people have died doing it. Go for the cordless... Or justwatch the great show instead.

 

[frankiee]

Thanks for the frank answer about the battery radio. I should get batteries.
I think I remember the rumor had something to do with the electrons in the up and powered T.V.
I think people thought that the electon gun of the T.V. caused a potential difference that would attract the lightening.
I think that if I turn the device off, that should be good enough because the circuit is broken and has no where to go (because open switch)
I dont go around unpluging stuff except my computer cable connection.
Come to think of it,why dont I unplug the T.V. cable??
Oh well, if a device fries, it fries.
I think I will look into insurance.

 

[frankiee]

itsmoked
I just seen your post after I posted the above.
You're right. Lighting is very high voltage and a switch is very small in comparison.
Thanks for the heads up about the phone. I would have never thought. I will tell my family.

So I take it that the phone lines are not grounded before they enter the house or are they?
Do telephones have some kind of insulation rating that they have to adhere to??
Thanks again. I'm going off to goggle things now

 

[itsmoked]

frankiee; Yes all phone lines have lightning arresters all over the place and at every house but nevertheless someone "gets it" every year. This is because something is faulty or the strike is just too close to be fully handled by the arresters.

 

[Skogsgurra]

Re: Arresters

A good clean hit near a (rural) telephone line induces so much energy in the telephone line that it will clean out everything - including arresters. The remaining energy is more than sufficient to kill anyone holding the phone.

We have designed a little device called "the Cottage Guard". It is connected to the telephone line. It has a PTT style gas discharge 230 V voltage arrester and is isolated in a sturdy plastic box. In spite of that, we receive many that have more or less exploded from lightning energy. The reason they explode is that the box is closed and rather small. A TV will not explode since there is more ventilation openings that release the pressure.

Gunnar Englund

http://www.gke.org

 

[DanEE]

Seems like every place I read a thread about lightning, there are always the statements made saying "nothing is effective" against lightning. These statements are particularly out of place in an engineering forum..

How is it then that TV transmitters sites, cell sites, etc. stay up and keep running in spite of direct hits..

I've installed and been maintaining equipment on a 1360 foot tall TV tower over a 10 year period that I'm sure has had many direct hits over the years.. and no outages due to lightning.

Unfortunately, the "GLEP" as it's called, the publication titled "The Grounds for Lightning and EMP Protection" written by Roger R. Block and founder of the Polyphaser corporation is out of print.. This document is worth its weight in gold when it comes to understanding how to engineer effective lightning protection.

The link below is the only document I've been able to find that has just a little bit of the info contained in the above document.

http://www.arrl.org/tis/info/pdf/0208053.pdf

Guess I'll start storing my copy in the bank safety deposit box.

Polyphaser is highly respected in the communications industry for the effectiveness of their products.

http://www.polyphaser.com/kommerce_products.aspx

I've taken a direct hit to an antenna at the house that burned off the connections to the antenna, but there was no damage to the equipment connected to it at the time, thanks to an installation and protective devices installed per Block's document above..

 

[IRstuff]

The other two parts of the article can be found here:

http://www.arrl.org/htdig/?method=and&words=lightning+protection&x=8&y=9

TTFN

 

[Skogsgurra]

DanEE,

There is a big difference between a TV tower or any similar structure and the common telephone line.

The main difference is that there is bonding and grounding of the structures as well as coaxial construction and spark gaps designed to take a lot of energy. None of these exist in a standard telephone installation. That's probably why you hear that "nothing is effective against lightning".

You haven't heard it in this thread, though. All that has been said in answer to a question about TV sets attracting lightning is that they do not - at least not more than other electric devices. And that an unprotected (or protected with "consumer quality" devices) telephone or terminal can be lethal to handle during a thunderstorm. And that is true and should also be told in an engineering forum.




Gunnar Englund

http://www.gke.org

 

[DanEE]

... or protected with "consumer quality" devices...

agreed!.. I'm appalled by the use of plastic housings and other weaknesses on some of these protective devices as mentioned in the part 2 article in the link posted above.. thanks for the link IRstuff!

I had one of the best I could find "consumer arresters" on my DSL line due to Polyphaser not making a suitable DSL line protector (i.e. let through voltage high enough for ring voltage AND the needed 1mhz bandwidth for DSL).

and it was just a matter of time before I lost the first modem due to telco line ground shift from a nearby lightning hit..

Afterwards I decided to try a Telco trunk model of IS-SPTL (shown in the part 2 article link above) in spite of the audio only bandpass rating. It works..guess not too great of high frequency attenuation and I'm on a short 1/2mile local loop.

btw, the application page for this protector shows a photograph of the unit being tested with a 40k amp surge! The 24AWG phone wire is vaporized off the unit by the 40kA hit on the input side yet, the measured output doesn't exceed the spec'd let through voltage.

pretty impressive!

 

[IRstuff]

The only time I've seen lightning get attracted intentionally is on NOVA, where the crackpot scientists actually launch a wired rocket into the clouds to attract lightning strikes. Even then, it's hit or miss ;-)

In any case, this is rarely a problem in So. Cal, at least in the coastal plains. We get maybe 1 lightning storm every couple of yrs. The mountains and high deserts get a lot more action.

TTFN

 

[MacGyverS2000]

As someone who once attended classes in the same arena as those "crackpot scientists" (University of Florida, Dr. Uman), I can say their setup is utterly cool in its simplicity. Not much more than a model rocket is used (OK, it's 5-6' tall, but not much more than an Estes model rocket in construction) trailing a thin wire. They wait for a minimum of charge to build up in the area, then let 'er fly! No, it doesn't always work, but it's much better than a 50/50 chance.

Dr. Uman (or maybe it was Dr. Rakov) has a nice chunk of crystallized sand/silicon (fulgurites) about an inch thick, but hollow, like a silicon tube. Nice looking display piece created by the lightning strike spreading out among the sand.

Dr. Uman consults for Vaisala, whose system is used by the National Weather Service here in the U.S.

Here's a short article about the rocket setup...

http://www.google.com/url?sa=t&ct=res&cd=4&url=http://

http://www.space.com/businesstechno...ghtning_030130.html&ei=U9gHQ-OiPMnc4QHP3syYDg

Dan
Owner

http://www.Hi-TecDesigns.com

 

[itsmoked]

Model rockets... wire...lightning storm.....

I always think.. "I wish I thought of that!"

 

[VEBill]

Lightning protection experts often overlook the fact that their professional work involves - almost exclusively - systems being installed into metal buildings or huts where good quality entrance protection systems can be made to work nearly perfectly. Ideal 'Faraday Cages' in almost every case. Another helpful circumstance is that the equipment is typically installed into single rack.

When you have a good Faraday Cage, effective lightning protection is actually very easy. It can even be made to work in the absence of grounding, as with airplanes.

One of my pet peeves is suggesting that the same 'entrance protection' systems for lightning protection can be made to work to the same degree of protection when the systems are normal consumer grade and installed in various widely separated locations around the home, interconnected with fairly long wires, in a typical wooden-construction (RF transparent) house.

My opinion is based on real world experince where I've had several instances of equipment damage where the common factors include lightning hitting a nearby tree (obvious location - trust me...) and the damage occured to circuits connected to long (the longest) INTERIOR wiring (nothing to do with any outside wiring).

Entrance protection on a wooden house might certainly help in preventing fires, but a direct hit flowing down the antenna lead in will almost certainly induce 'minor' failures into anything electronic connected to longs runs of interior wiring.

Does anyone seriously think that a consumer grade TV is going still be working after a direct lightning hit onto the outside antenna - even if the cable is connected to a protection device and well grounded? Unlikely to be working, but at least it won't explode. It might even be repairable.

This is why it is a perfectly reasonable simplification to say that "nothing is effective" against lightning damage.

Unless as Step 1, you build a metal house...

 

[DanEE]

Actually the GLEP referenced above, shows how to do "birdcaging" of wooden structures.. Old fashion, but good lightning rod installations were the first to do this..

and the reference to the longest interior conductor indicates magnetic coupling or ground shifts are the likely culprit.. especially if there are multiple paths to the device on the longest interior conductor..

I made the same mistake years ago before learned more about the subject. I had unknowingly installed my TV in a guaranteed blow up situation with the power (and service entrance ground) coming from one corner of the house and antenna (and outside ground '68 feet away at far end of the house. And of course the flashover point between the two paths would have been on the circuit boards inside the TV.

In a lot of cases, you can't move or change the entry points to get rid of the loops, but by adding a common ground plate at the device with power and antenna protectors on the plate the flashover point is now inside the protectors. The TV now being on a stub, will only see the let through voltage of the respective protectors. While still on the loop, it could experience a ground shift voltage rise as a unit, but not major current through the device.

Many commercial sites have the same problem, simply because the area of interconnected equipment is so large, you have to be concerned about loop susceptability to magnetic coupling and ground shifts.. The TV transmitter site I mentioned in the first post is a brick building no faraday shielding inherent in the building.

I have the following on my wooden house now, I'm sure not fail safe under all circumstances, but "better than nothing"..

Lightning rods, a partial perimeter ground to various distributed ground plates and for tie down grounds from various ham antennas. All bonded together as recent NEC codes now clearly state and making a fairly decent birdcage without inordinate expense.

One known direct hit on an antenna with no damage other than the antenna itself.

 

[VEBill]

"...not fail safe under all circumstances..."

That statement represents a position that most reasonable people would agree with.


At the risk of beating a dead horse, compare the following:

1) A SW radio connected to a random wire antenna that goes up to the eve and out to a pole with a total length of about 100'.

2) An AC adapter powered telephone device connected to a unshielded telephone cable that goes up to the second floor and across to the other side of the house with a total length of about 100'.

In the first case, everyone 'knows' that you should provide entrance protection and grounding to help protect the radio in the event of a local strike. In the second case, everyone (including experts) pay it no attention whatsoever because it is 'inside' the (wooden) house.

 

[RobWard]

If you are really concerned about a TV exploding after a lightning strike, the simplest remedy is to buy one that's already been struck, and repair it, then it's totally lightning proof isn't it?
After all, you know what they say about lightning...

"I love deadlines. I love the whooshing noise they make as they go past." Douglas Adams

 

[weldtek]

macguyvers2000, sounds like a 'fulgarite'

 

[MacGyverS2000]

I can't claim one spelling is correct, all I can say is anytime I see Dr. Uman's name associated with a story the spelling is with two u's. The spelling with an 'a' seems to be associated more often with amateur lightning sites or rock/gemstone sites. <shrug>


Dan
Owner

http://www.Hi-TecDesigns.com