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#129555 - 04/23/05 07:27 AM Lightning Theory  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,223
SI,New Zealand
I'd like a few of you fella's to help me here.
It is a well known theory amongst us free thinking people that lightning does not merely strike the ground as a source to earth.
My experience with high voltages and also things I have seen on the Net, would suggest that there are "feelers", that run from the ground upwards, to where a direct strike will hit.
Hence golfers being hit, the time between the feeler going up and the actual strike is measured in Nano-seconds.
Does anyone prescribe to this same theory?.
Lightning is a nasty thing, the more we can do to keep it away from our houses, people and anything else that affects our lives,the better.
Mind you though, Lightning really only became a problem once we started having Electricity in our houses and with using metallic building systems.
Please feel free to put your spoke in here.

Mike.
[Linked Image]


Tools for Electricians:

#129556 - 04/24/05 04:22 AM Re: Lightning Theory  
Alan Belson  Offline
Member
Joined: Mar 2005
Posts: 1,803
Mayenne N. France
Trumpy
You've got it about right. Negative charges build up in the cloud base, while positive charges build on the ground. The + charges tend to collect and extend up round high points in the landscape; trees, masts, people, buildings. The -ve cloud charges extend down as leaders, some 100-200 feet, and when one of these gets near enough, a surge of + charges rises to make a channel- this channel then triggers a current flow from the ground, provoking the lightning return stroke proper. So, do lightning rods on buildings serve the purpose of grounding the +ve charges to reduce the chance of a strike? I've always thought; how can a puny strip of copper running down a building carry the hundreds of Megawatts of a bolt?
Alan


Wood work but can't!

#129557 - 04/24/05 04:36 AM Re: Lightning Theory  
Alan Belson  Offline
Member
Joined: Mar 2005
Posts: 1,803
Mayenne N. France
sln.fi.edu/franklin/bells.html

Ben Franklin provided the answer in 1753!!

Alan


Wood work but can't!

#129558 - 04/24/05 10:09 AM Re: Lightning Theory  
Dnkldorf  Offline
Member
Joined: Dec 2004
Posts: 1,064
nowhere usa
Trumpy, here is a very basic site that explains what happens, but like I said, very basic, it's atcually done for kids to understand.
http://skydiary.com/kids/lightning.html

Alot more goes into how, why and where lightning will strike.
Stuff like ions,isokeraunic levels, inductance, ect..

Roger Block's book is awesome on this, if you have the time to read over and over again. It's kinda confusing.


#129559 - 04/24/05 10:18 AM Re: Lightning Theory  
Dnkldorf  Offline
Member
Joined: Dec 2004
Posts: 1,064
nowhere usa
Another note on this,

The old saying "lightning never strikes the say spot twice", isn't very true.

I rememmber reading that lightning strikes the Empire State building an average of 30 times per year.

If I can find that link, I'll post it.


#129560 - 04/24/05 05:21 PM Re: Lightning Theory  
Alan Belson  Offline
Member
Joined: Mar 2005
Posts: 1,803
Mayenne N. France
Dnk..
Thanks for that link, I never realised that the actual flash went upward,which goes to show you learn something new every day.
Blinking science teachers!
Alan


Wood work but can't!

#129561 - 04/24/05 11:28 PM Re: Lightning Theory  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,708
Anaheim, CA. USA
Lightning is so very interesting!!!

The Elect. Engineering Manuals Sittin' Up On My Shelves - Collecting Dust each have an entire section devoted to "What Is Thought To Be Correct - So Far" regarding the phenomena.

Stroke Leaders "Pop" out from both sides - downwards from highly negative charged Cloud formations, and upwards from Earth bound areas of high Positive charge concentrations.

The Earth bound surface areas directly below the Cloud mass become Positively Charged, due to the increasing Negative Charge levels "Pressed Against" the Earth areas, from the Cloud mass above.

Negative charges in the ground areas are repelled away, leaving Positive charged moles O' dirt (and attracting additional Positive charge carriers).

All this increases until the dielectric strength of the enviromental Air gets punctured - then at least two stroke leaders connect, resulting in a discharge path.

The connection brings in an initiating arc, then the Plasma is developed. The Plasma is commonly oriented in an increasing "Step" from Ground to Cloud (appears to begin at the ground and "run up to the cloud"), whereas the initiating arc pulses downwards from the cloud.

The arc comes first, then the Plasma is created - which "Pushes" against the surrounding Air as it increases in size, and consequently as it decreases in size, the Air rushes into the void space.
That's where the thunder comes from!

If you are in the field of influence prior to a discharge event, you will feel its Capacitive field effects (hair will stand on ends).
That is the time for you to hit the floor!!! [Linked Image]

To sum things up:

Water "cracking" into Ice when it freezes, generates the abundant Electrical Energy
(actually there are some other factors - even discharges from ABOVE the Stratosphere Clouds shooting downwards to the cloud mass, but too much to cover!).

The Charges in Cloud masses become oriented with Negative ones towards the bottom of clouds, and + towards the top.

Charges increase as more Ice cracks from Liquid Water (the water loses a small mass when becoming solid - hence the resulting energy "output").

As charges increase in the clouds, the ground plane becomes the "Opposite Plate" of the "Capacitor" and has a resultant "+" charge.

As the charge levels become high (+2 to +5 KV / Meter), "Stroke Leaders" begin to "Reach" towards the opposite polarity (up from ground, down from cloud). The entire event is similar to a Capacitor - with the cloud base being the "-" abundant plate, the Earth being the "+" abundant plate, and the surrounding air being the "Dielectric" between the plates.

When the field strength / charge level, develope to a point which results in a potential difference of +15 KV / Meter, stroke leaders are long enough to make connections.

Many leaders connect, but the ones of best conduction result in the visible event blasts.

At the point(s) of highest conduction, the initializing arc "Smacks Together" via the leaders - tearing the dielectric strength at that location.
This is usually heard as a "Loud Hard Clap" followed with a "Ripping" like sound.
The rip sounds like it is coming down from the clouds.

After the arc is setup, the Plasma begins its "Pulses" against the surrounding air.

The Plasma pulses rise in strength, become somewhat stable as the charges begin to flow easilly, then as the clouds' charges decay, the pulses lose strength and eventually cease all together - marking the end of that complete event.

Plasma pulses may range from as little as 10, upto hundreds per an event.

As the Plasma flows, it makes a more conductive path, so more charges flow.
As more charges flow, the Plasma becomes more conductive path, so it increases in size.

The Plasma pulses outwards in strength against the surrounding air - which keeps it "In Check", and has an energy transfer involve (compressing the air requires energy - and the resultant sound generated - the Thunder, also requires energy).

When the energy state become "Neutral" (or at least close to it), the event is complete.

The entire process repeats as needed per imbalanced energy levels are developed.

Sorry to throw in such simple and quick & dirty descriptions here.
Also, my descriptions are somewhat "odd", likely due to it being years since I've discussed this stuff!
[Linked Image]
There's TONS more to study in this area of theory, so have fun!

Scott35


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#129562 - 04/25/05 01:09 AM Re: Lightning Theory  
Alan Belson  Offline
Member
Joined: Mar 2005
Posts: 1,803
Mayenne N. France
But not with a kite.
Alan


Wood work but can't!

#129563 - 05/01/05 03:27 AM Re: Lightning Theory  
Scott35  Offline

Broom Pusher and
Member
Joined: Oct 2000
Posts: 2,708
Anaheim, CA. USA
***Bump***

Bumping thread to life.

BTW: Mike (Trumpy);
Did any of the stuff I posted make sense? [Linked Image]
Was any of it helpful / enlightening (sp??)?

Scott35


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

#129564 - 05/01/05 10:42 PM Re: Lightning Theory  
Ron Braggins  Offline
Junior Member
Joined: Apr 2005
Posts: 2
Aylesford, Kent, England
My understanding follows somewhat as Scott put it, as follows.
In a storm, clouds rotate much like a generator producing AC, and a state of strain exists between the top + and bottom -of the cloud formation (capcitor effect).With AC, the + end is short of electrons, so when the dielectric breaks down, the + end gets its supply from the - end, the strain is relieved and a flash results.
In other situations, a state of strain also exists between the clouds and the ground, which has an even greater supply of electrons, and when this strain breaks down, a strike results - logically from the ground up. We see the strike moving downward, but I believe this is due to the illumination of the ionised air - not the strike itself.
I take the point re the small strap of copper lightning conductors - and Ben Franklin's sterling work, which I assume took place during a quiet phase in the affairs of state - but they seem to work satisfactorily - and it is interesting to note that other skyscrapers in the area may not need to bother with lightning conductors as they can rely on the Empire State attracting any wayward strikes!

Hope this helps.

Ron Braggins - England


Ron Braggins

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