TRactors and lightning

[Kubota-monkey]

These past few days the cold fronts and warm fronts have collided over my state and have produced some frequent t-storms. Now they seem to appear unexpectedly and I always seem to be caught out in the middle of it. The tractor engine and ear protection prevents me from hearing those loud boomers from far away.


I will get to the point- If a tractor is hit by lighting, is the operator safe like we are in a car or is it a serious hazard?
Happy TRactoring and play it safe-

 

[Roy]

I see two different answers. Since a tractor has rubber tires, I guess minimal ground potential (arc only), thus not an extreme hazard (but the potential is not zero, so there is still a risk).

But if a loader or implement is providing ground contact, a tractor presents a hazard which cars do not. Currents flow on the outer-most surfaces of any conductor (points farthest from the geometric center). When you're in a car, the current will travel around you. Take away the roof structure, and now your body and head now provide part of that outer-most structure.

 

[W5FL]

Just always remember that your odds are considerably better to get killed by lightning (not just hit) than to win the Texas lottery. Buy tickets accordingly. More people are killed by lightning each year than in all the tornadoes and hurricanes and all other weather related events in the US.

You are NOT safe on a tractor. When you detect lightning try to get you and the tractor in the barn. It is unusual (but not impossible) to have severe lightning strikes without also having rain which make you a well grounded target! /w3tcompact/icons/frown.gif

I had lightning hit our TV antenna when I was sleeping immediately under it in the house. It ran down a guy wire, hit a trellis wire and ran over 100 foot, knocked a 1 sq ft hole in the house, knocked the kitchen cabinet off the wall, jumped to the sink (which was grounded) and melted the lead out of over 100 foot of cast iron drain pipe. Wicked little stuff ain't it. /w3tcompact/icons/frown.gif

I now have a 66 ft antenna tower that sets on a hilltop. It gets hit by lightning regularly. Sure makes a lot of noise, but it is well grounded and no damage is done. A friend's father was killed by lightning when he walked out of the house to simply roll up the windows on his car.

 

[Bird]

Whew, compared to you guys, I've been lucky!/w3tcompact/icons/smile.gif One little lightning flash last year did kill one TV, one satellite receiver, two telephones, one lamp, and one alarm clock for me.

Bird

 

[MChalkley]

Statistics is an odd science. I've always maintained that, for most folks, winning the lottery would cause them to get struck by lightning within a few days' time.

Mark

 

[KCB]

You're probably at a fairly high risk if you're sitting on a large metal object, usually grounded by an implement, and out in the middle of a field. Maybe worse off than a golfer (I think this is Gods' way of punishing these guys for having too much leasure time). As well as a person may be protected in a car because of its faraday cage effect. Although rare, people in cars have been struck by lightening, as have people sitting in their houses. The guy in our FCC lab says that you can get struck by lightening almost anywhere. Some places are just more susceptible than others. N.C. is second only to FLA. in lightening related deaths, so it always bothers me when someone tries to de-emphasize your chances of dying from something by comparing it to your chances of getting struck by lightening.

 

[W5FL]

If you study lightning from a standpoint of protecting towers, radio equipment, and electronic equipment, you can simply consider it as a current source that will make all the voltage that it needs to jump the gap. It will jump the gap whether it is 1/16 inch or 10,000 feet. There is a lot of difference in the sound although the current flow is the same. One will just go snap and the other creates tremendous local heating and becomes a strong clap of thunder.

People used to have a lot more sense, but they have lost it as hundreds of thousands of people have moved to the rural areas. There WAS a reason why houses had lightning rods and they need them just as much today as they did then. People used to fear thunderstorms but many now just pay little attention until it causes death or a lot of damage. National Weather Service continues to correctly warn people to seek shelter when there is a severe thunderstorm warning.

 

[MarkV]

How effective are lighting rods on a house? We have considered them. You don't see to many, in our area, and I have had people say they just don't work well enough for what a system cost. Anyone have any information?

 

[W5FL]

I plan to add them to my house and barn. There is info on the web, but it is not very straighforward. If I find any more info on it I will post it in the Rural forum. They are effective. You can't build a building over 3 stories without them. Look closely and you will see little sharp points on a lot of structures. The reason people say it is not worth it is their attiutude is insure it and let someone else worry about it.

I live on a hill top location about 400 ft above Fort Worth. The insurance company will only pay off once. The second time they will cancel your policy when they pay that one. Their reasoning is that you seem to be in an area that is more apt to have continuing claims and we can't make any money that way.

 

[Anonymous Poster]

It is my understanding that high frequency currents (AC) tend to flow more on the conductor surface then center. Supposedly, low frequency A/C and of course D/C currents, are not that partial. This is one of the reasons, besides flex, that multi-strand conductors are used on hi-fi equipment.
Now, is lighting's EMF pushing an A/C or D/C current??
regards,
george

 

[W5FL]

Yeah, but those are mainly marketing hype. Nothing in the audio or ac voltage range applies to skin effect and flex is the only reason. RF voltages above 1 mhz starts to make a small difference, that is why hf connectors are silver plated (gold plating is for marketing purposes). At TV frequencies, skin effect is significant.

Lightning is DC but has a very fast rise time to the current waveform.

 

[Trvler]

If you've ever witnessed someone killed by lightning.. or understood that lightning can strike an object over 100 miles away from the storm, you'd never ask that question. When lightning strikes, get someplace safe. QUICKLY!

 

[TomG]

Yes, that's my understanding. The relative safety in a car is because you're in a steel box, not because the car is on rubber tires. At lightening voltages, everything is a conductor, and so everything is always grounded. Current always takes the path of least resistance. In this case, from the ground, arcing to the wheels, then through the body and off the roof.

An occupant in the car can be surrounded be extremely high voltage, but it's the same voltage all around. Within the car, there's little difference in potential. Still, within the car, advice is that metal parts should not be touched.

 

[KCB]

Lightening is a fast, complex AC pulse, not DC as is commonly assumed. Same for ESD, or electro-static discharge. Because of "skin effect" (lightening is thought to vary in frequency from 20khz to 500 khz) grounding cable should be stranded, to increase surface area, and have no sharp bends, to reduce inductance. A single point ground is best, to avoid ground loops.

 

[TomG]

If I understand the idea of lightening rods, it's that they provide low resistance paths around objects on the ground. Damage occurs when current travels through, for example, a tree (the sap boils) or jumps within a house.

My inexpert opinion is that the need for lightening rods is somewhat less important today, because the electrical service grounding is a fairly good lightening rod. The service ground, combined with codes that require bonding of metallic plumbing to the service ground buss, provide low resistance paths within a house. However, lightening rods still should improve safety. It is important to bond plumbing, well casing and metal drainage pipes to the service ground buss.

I use a more modest technique than a lightening rod system. I place grounding plates or rods on the opposite corners of a building. The second plate is a part of the service ground, or they can be a supplemental grounding system on buildings served by branch circuits.

The idea is that a strike to one side of a building draws current from a sizable ground area. The huge voltages can create differences in potential that result in jumps within the building. The idea of the second plate is to provide a low resistance path around the building and reduce potential differences within the building.

My electrical inspector did say that there is no research that proves this idea works. However, the technique is farily commonly held, and it isn't likely to hurt anything. Any actual research probably would be inconclusive since the number of instances would be small and the number of factors affecting each particular instance would be large.

 

[roysallis]

Do you know why lightning doesn't strike twice in the same place? It doesn't have to.
Seriously, some people think it doen't strike again in the same place but this belief is not true.

 

[TomG]

Definitely not. When I was dating my wife, we used to watch storms from her apartment in Toronto--just to see strikes on the CN tower. At the time the tower was the tallest freestanding structure in the world. I think it typically was struck in the hundreds of times a year.

 

[W5FL]

Since we are this far off subject anyway....

Polyphaser has done more research in the field of lightning protection for electronic equipment in a structure than anyone else that I am aware of. They produce an excellent book called Grounding Systems and sell everything from entry panels to lightning arrestors for all types of commercial communications equipment. They do not sell external structure points or cabling, but others do. It is very interesting reading. My interest is because my antenna tower gets struck a few times a year and it and the equipment are properly protected with over a 1000 feet of ground wire and ground rods and it always survives. There are many advantages to living on a hilltop, but weather is NOT one of them.

 

[KCB]

Sorry, I thought I had posted this information earlier. Anyway, I spoke too soon about lightning being AC or DC. Our FCC guy says it is a fast transient static discharge. I have attached addresses for some interesting info about the subject.

http://www.lightningsafety.com/

http://www.amasci.com/emotor/statelec.html <-- lots of links and leads to:

http://www.eskimo.com/~billb/miscon/curstat.html

http://wvlightning.com/index.html