earthing. the ECMag article

[K8MHZ]

Lighting....upward strikes.........

http://www.youtube.com/watch?v=RDDfkKEa2ls&feature=related




groovy stuff


Step leader...............


http://www.youtube.com/watch?v=6MUYsIjTKvk&feature=relmfu

It actually goes both or either way.

I am involved with the National Weather Service through an effort called 'Skywarn'. It's for weather spotting (not chasing). We get to go to weather classes put on by the NWS each year. Lightning is a very well covered topic and the collection of lightning videos and photographs they have is astounding.

One of my favorites is watching as a bolt hits a power pole that is equipped with one ground rod and #6 solid CU connecting it. The #6 literally vaporized. It was like a filament in an old flash bulb.

We don't charge for Skywarn classes, I don't think the NWS charges for them anywhere. If you are interested in lightning, get in touch with the NWS and ask when and where their Skywarn classes are and if they will be covering lightning.

 

[K8MHZ]

I think one other detail here is static electricity dissipation. Some things pickup static -- rotating machinery, even wires in the wind. You don't need a low resistance path to discharge this, as any person who has touched a charged plastic item while wearing tennis shoes on carpet can discover. But you need something or else you can get bit from either wire or chassis. I believe static wristbands for electronic static stations have about a 10K ohm resistance in them.

Connecting the EGC to earth can dissipate any static that has built up on an object -- seems like an easy way to do it as long as that bonding conductor hits the earth at some point. A ground electrode conductor or earthing conductor would be a better term, but implies a separate conductor.

Some cars are prone to this too, and you can see a strap hanging under the car dragging on the ground to dissipate it out. We even have a utility cart at work that was always shocking us (I think it was the tire material used). We hung a 1' piece of braided conductor under it which drags on the ground and now no more shocks.

What you are describing is actually 'ground to ground lightning'.

I am surprised you know about static build up on wires. Ham radio operators have to deal with that in dry areas. A long wire used for HF can gather enough charge to snap you pretty good if not grounded for bleed off. That static is also hard on the equipment.

New Chryslers used to come with Invicta tires. They were soft and wore out quick, but they made a brand new car's ride better. For some reason they also promoted static build up. We replaced many a computer in the early 1990's because of it. I remember touching a new LeBaron in the lot one day and getting snapped so hard it hurt. Customer complaints abounded until the factory figured out that a different tire composition would eliminate the problem. Putting static straps on brand new luxury cars was not going to the the answer.

 

[jwelectric]

Excellent point. My question is, how does two ground rods in sand limit voltage? Oh, and voltage must be measured from two points. Which two points are we supposed to limit voltage from when we ground our systems?

this is a good read on the subject
www.barefoothealth.com/science/global_electrical_circuit.pdf

 

[K8MHZ]

this is a good read on the subject
www.barefoothealth.com/science/global_electrical_circuit.pdf

That's a lot of read, too! 96 pages.

Thanks, I glanced through most of it. I almost didn't as the opening was going on about health vs. the human body being grounded.