Energy from the Ground - Self powered generator by Barbosa and Leal

[a.king21]

Milehigh: we could do with your electrical knowledge input here:


https://www.youtube.com/watch?v=lGIJSWirhPw

[Farmhand]

Looks to me like Tesla showed/used the single wire Earth return in the patent below but he doesn't lay claim to the idea so it seems the principal has been around for a very long time. Pre Tesla.

Tesla Patent.
http://www.google.com/patents/US593138

Others have implemented it in modern times, we use it in Australia and it is not as safe as they make out. A SWER line was responsible for a very bad bush fire that killed a 173 people and destroyed many properties.

It happens when the HV line comes down but does not actually trip the breakers and such, this leads to the line starting a fire through a resistance.
If the line comes down on trees the resistance can be too high to trip the breakers or whatever and the tree can catch fire due to the current through it.

The Royal Commission concluded that five of the major fires that it investigated were started
by powerlines
2
. In its July 2010 Final Report, the Royal Commission concluded that
3
:
The SWER and 22kV distribution networks constitute a high risk for bushfire ignition,
along with other risks posed by the ageing of parts of the networks and the particular
limitations of SWER lines.
The Royal Commission made 67 recommendations, of which eight (Recommendations 27 –
34) relate to reducing the likelihood of powerlines starting catastrophic bushfires. These
recommendations have been accepted by the Victorian Government.

Powerline bushfire report.
http://www.esv.vic.gov.au/Portals/0/About%20ESV/Files/RoyalCommission/PBST%20final%20report%20.pdf
..

Lightning strikes to trees can leave behind trees that are half dead and half alive, like one side of the tree will die but one side can live, such a tree would be great for starting a fire, maybe even a dead or a live tree can do it. I see no real world tests on this.

..

SWER lines can also produce potentials along the current path of up to 40 volts per meter or so at the ground surface, and I read a article that warns of possible dangers to livestock. If a human walked in bare feet on the wet ground in the line of the flow of current and took a long step the person might be able to feel the up to 40 volts 50 Hz AC first hand.Livestock have a longer gait than a human can be over 1 meter.

..

I think the words should be that "It can be safe", but there is 170 odd Australians that also say it can also be very deadly and destructive.

..

[MileHigh]

Farmhand:

That is a very unfortunate story.  Note that regular power lines could also short with trees and cause fires.

The real issue is that it was a design and/or implementation or verification or maintenance failure and a person or persons could be legally liable and subject to criminal prosecution.  Somebody signed off on a drawing and then it was implemented in the field.  Presumably this was a civil or electrical engineer.  They also had to visit the site and approve the construction and sign off on that also.  Then there is a maintenance log book somewhere.

I am just making assumptions and I am not going to look up the story.  But people were the true source of the problem.

MileHigh

[MileHigh]

Pop quiz no Googling:  If there is a break in a long distance transmission line, how do you find it?

[Pirate88179]

Pop quiz no Googling:  If there is a break in a long distance transmission line, how do you find it?

By the fire?  (Follow the smoke)

Just kidding.

By "you" I assume you mean the power company right?

If the line has not shorted out and blown something on either end of the circuit,  I assume they could test the resistance of the two parts and with some math, determine how far down the line the break is.  (Total guess here)  They already know the wire diameter and ohms/foot.

Bill