Hi MikeML,

I'm not sure what you mean with over promoted and over sold. Can you please explain.

 

Hi MikeML,

I'm not sure what you mean with over promoted and over sold. Can you please explain.

The guys that sell these things lie about their effectiveness

 

In an area prone to heavy lightning storms - like my place - if you do not have lightning rods, [[ no one around here does - I may start a fad ]] there is NOTHING that will protect completely from the ferocity of a lightning bolt.

I mentioned the corona accompanying a bolt being similar to an electromagnetic pulse weapon when lightning actually strikes > this appears to be true...
I went -a - Googling... there is a ton of studies / papers on the subject - enough to keep a physics student busy for quite awhile..

 

Hi MikeML,

I'm not sure what you mean with over promoted and over sold. Can you please explain.

A plug-in type protector inside your house is just another antenna for the lightning pulse to induce energy into if it's not properly connected to a central grounding point.
Most just can't work plugged in at a wall socket unless they are part of a layered protection system. You need to reduce the energy gradient near and inside your house first to a level that they can handle , to do this effectively with the large amount of energy from a strike you need to direct that energy into earth with a low Z connection to reduce the EM pulse field inside the house wiring. If you don't have a good ground sink for the energy to go it will just find the next best point inside something you value. Reduce the energy gradient inside your house, direct most of it outside if possible and away from inside sensitive electronics with good single point grounding. (all inside/outside wiring grounded/surge protected at a 'outside if possible' single point) Inside the voltage gradient from EM pulse effects between close points on power connectors should be small if they all have the same reference to ground so lower energy common-mode voltages are less likely to cause damage and can be handled by local protection circuits.

 

Mike,

Many thanks for your reply. I'm getting it now

 

packratking

What is lightning rods, is it the same as earth spikes

Possibly... L. rods, are the devices resembling a radio antenna you see atop things like barns and houses in rural areas like farmland. Also on some cell towers

They aren't specifically designed to attract lightning, simply someplace for a random bolt to discharge relatively harmlessly.

Also something Obama should carry with him at all times on the golf course !!

 

Interestingly enough, lightning rods help to eliminate direct lightning strikes.

They create a corona discharge that prevents the potential difference from building up too high.

 

Interestingly enough, lightning rods help to eliminate direct lightning strikes.

They create a corona discharge that prevents the potential difference from building up too high.

That is debatable. I believe that an elevated lightning rod is more likely to attact lightning, i.e. increasing the probability of a strike. The goal is to make the strike less destructive than it would be without the lightning rod.

The primary purpose of a lightning rod is to create a conductive path (almost a short circuit) from the tip of the rod directly to the earth below the structure being protected. The conductor is usually a bare #10 or larger Copper wire connected at one end to the rod, and at the other to one or more 8ft copper-clad ground rods driven into the earth. It is routed on the outside the structure being protected.



You have all seen the damage done to a tree when lightning strikes it:

The damage is caused by the 40,000A lightning current pulse flowing in the moist wood just under the bark. The power dissipation (I^2R) turns the moisure to steam, instantly blowing the bark off the tree. If the lightning strikes your stick-built house, the same thing happens. It literely blows the wooden structure apart, possibly starting a fire in the process.

Running the grounding conductor on the outside of the building keeps the current pulse outside the structure. The Copper conductor has an impedance such that it lowers the voltage gradient between the tip of the rod and the earth below.

 

I understand the principal of directing the strike into a controlled path to a point in the earth rather than letting the charge decide it's own path.
I think that's the idea behind lighting rods, a heavy conductor and a ground rod or buried plate.
Which makes me wonder just how to keep the lightning charge that enters the earth through the ground rod from simply coming back up the other mandated ground rod which is bonded to the neutral at the service panel. Many of todays electronics devices have only a connection to one leg and the neutral. And all of the circuit grounds are grouped into the bus right along with the neutrals in the panel. I watched a documentary about lightning that stated it may be a billion volts at 100,000 amps and it moves through miles of air. The IC's are sitting ducks as far as I can reason.
How wrong am I on this?
All the best.

 

As a ham who has a 60 ft radio tower I have studied this question. The best guidance I could find says it is a bad idea to have the radio tower on the side of the house away from the side that has the electrical service entrance, because if either the tower or the power pole is struck, then the surge flows through the house wiring (in either direction).

I was able to locate the radio tower about 6 ft from the service entrance.
The radio tower has four ground rods around its base. I was able to run a grounding strap from the base of the tower over to the electrical panel ground rod, so all five ground rods are on the same side of the house.

 

Mike

Thanks for all the pic's and info. Now i'm a bit better off knowing what can happen.Luckily for me is that i know all the copper pipes in the roof and even outside my house are connected to the ground rod (3meters long) with copper straps. I'm just going to add the lightning rod on to roof to play safe.

One never knows what can happen and then i'm at least protected in some way

 

That is debatable. The conductor is usually a bare #10 or larger Copper wire connected at one end to the rod, and at the other to one or more 8ft copper-clad ground rods driven into the earth. It is routed on the outside the structure being protected. ???

EGAD !! Are you sure of this ? Most all of the lightning conductors I have seen are done with several braided # 10's, resulting in something on the order of a 6 aught [ 000000 ] cable...

An amateur guessing, does the " skin effect " apply to that magnitude of volts and amperage ? and wouldn't the ground stake have to be solid copper ?

 

I dunno...seems like just providing a better path than the stainless steel chimney liner or the flue vent for the gas fired water heater is the goal. No matter what you use for cable, a "successful" capture of a direct hit is going to vaporize parts of the system. Still, I've seen public buildings with apparently undamaged braids going down the sides of them. I think regular inspection and maintenance is mandatory, no matter what you use for the conductors.

 

EGAD !! Are you sure of this ? Most all of the lightning conductors I have seen are done with several braided # 10's, resulting in something on the order of a 6 aught [ 000000 ] cable...

An amateur guessing, does the " skin effect " apply to that magnitude of volts and amperage ? and wouldn't the ground stake have to be solid copper ?

The more circular mills, the better. It depends a bit on where you are, and the magnitude of the storms. The peak current in a strike ranges from 10KA to over 200kA, in a pulse lasting about 40us. A #10 Cu wire is not vaporized by that pulse.

The advantage of more surface area has to do with reducing the inductance per foot of ground wire, meaning a smaller voltage gradient per foot. My radio tower, for example is about 16 inches on a side, and 60ft high. If struck, I calculate the peak voltage from top to bot to be only about 30KV; if the tower was a single #10 Cu wire, the voltage might be three times that.

I use the same 8 ft ground rods sold for electrical service grounding around the base of the tower. They are Cu-plated steel rods, about 1/2" o.d. They have to be steel to be driven into the earth; I think it wouldn't be possible to drive pure Cu rods (too soft).

 

The more circular mills, the better. It depends a bit on where you are, and the magnitude of the storms. [[ we get some doozies ]] The peak current in a strike ranges from 10KA to over 200kA, in a pulse lasting about 40us. A #10 Cu wire is not vaporized by that pulse.

It is said, lightning never strikes twice in the same place... I beg to differ... I have seen ground-strike bolts flicker in the same channel, for upwards of a full 1/2 second... Can a # 10 wire really survive 10 - 200 thousand amps for that long ???
I'm from Missouri... you know what that entails...

 

Just put a corroded connection somewhere in the ground wire if you want to guarantee fireworks.

 

It's not something I worry about in the UK I just carry on as normal and I've never had a problem.

On the other hand your thunderstorms are possibly more intense and your power grid a little less reliable?

A lightning strike causes extreme ground gradients, if it hits anywhere near the power cable that eventually gets to your house, the entire mains wiring of your house is elevated to a severe transient - meanwhile other services such as phone lines, water pipes etc nowhere near the strike are not.

A common phenomenon in rural areas is livestock (and sometimes people) are killed during lightning strikes by the ground gradient over the distance their feet are apart - women are OK however, they've got a spark gap.

 

Just put a corroded connection somewhere in the ground wire if you want to guarantee fireworks.

You ain't just a whistlin' dixie ANY corroded connection in the circuit will not survive...

As an aside, I and a couple of friends used to chase spots where lightning had struck the ground, to see if we could dig up the " Fulgurites"

 

You ain't just a whistlin' dixie ANY corroded connection in the circuit will not survive...

As an aside, I and a couple of friends used to chase spots where lightning had struck the ground, to see if we could dig up the " Fulgurites"

There's pictures lurking somewhere online.

Usually the fused glass "branches" are fairly bushy as the lightning branches out looking for the path of least resistance.

Sometimes you get a thick bough where the strike has found a buried power cable, just a few "twigs" branching out from those.