"What have you done with Bob " asked about reality and practicality of SWER power lines. __________ "SWER" power lines have a very long history and are highly useful. They still have some very competent protagonists and a significant number are still in use. Engineers will be aware of the two dimensional concept of "Ohms per square". If a 1 cm edge square of a given thickness of a uniform resistive sheet has a given resistance between opposite parallel sides, then a 1 metre edge square or a 100m edge square of the same thickness of identical material will have the same resistance edge to edge as has the 1cm edge square. This is obvious on inspection as increasing the dimensions scales up the path length and path width in equal ratio. The resistance of "ground" behaves similarly - here we are coupling into a half sphere about the end points and we must deal with 3D curvilinear cubes (rather that the more familiar 2D curvilinear squares) but the end result is similar. The main issue in connecting a high energy ground path between two points some km apart is coupling into the bulk ground at each end - the resistance of "the earth" is not a problem - attaching to it is. As Bob adumbrates, it is possible to make ground connections whose quality varies widely with local conditions - BUT 'we' have centiries of experience of creating reliable repeatable ground connections. All electric power administrations have procedures which are required to b followed to produce an adequate ground connection for a given taks under worst case conditions. The procedure do indeed superficially appear somewhat similar to phrenology but the comparison is illusory. Here the bumps on a head are replaced by soil types, water table, length and diameter and material of of grounding pipes, sacks of Bentonite, and more. The ground protection systems in Phase / Neutral / Safety ground systems in widespread use in many countries depends crucially on the ability to make and maintain an adequate safety grounds. The UK and NZ are two such - it seems 'from a distance' tat US practice may be less stringent with some systems. > Who says that the current flows deep under the ground (i.e., 1200m)? > Why doesn't it take the path of least resistance, like current normally does > (I've never seen it do otherwise in my entire life)? Here as in all systems, current flows in proportion to the applied voltage and inversely in proportion to the resistance the voltage is applied over. ie current does not take the path of least resistance but "takes the paths of all resistances" - from each according to its inverse resistance, to each according to its applied voltage. But, I know that you know that. The claim that current flow ***mainly*** at a depth of 200 feet is quite possibly correct and if it is, is liable to be caused by non linear compositions of real world strata and soil conditions forming a path of effective minimal resistance for power currents. material will certain On 5 May 2012 02:24, Bob Axtell wrote: > On 5/3/2012 3:27 PM, Martin McCormick wrote: > > Electron writes: > >> Won't the return currents cause ionization in the terrain, etc.. > possibily > >> with biological implications? > > I just red the pdf on the link and it did say that the > > return currents were around 1200 meters down. I know that > > alternating current is successfully used in meggers which are > > magneto-based ohm meters for measuring soil conductivity. I > > don't know what would happen over a long period of current flow > > but as long as there is not a DC component, the continuous > > reversal seems to prevent ionization. > > > > Neon and fluorescent lamps last much longer running on > > AC than they do on DC. Also, some en clinometers use an > > electrolyte in a sealed tube and they can be damaged by DC but > > work fine on AC. > > > > Martin McCormick > > WB5AGZ > I also read the PDF thoroughly. I am inclined to consider the idea of > transmitting > power through ground as unsound. > > I see that, in theory, current will pass through the ground. But will it > do so reliably? > Wouldn't the fact that soil holds a varying amount of moisture cause a > differing > amount of conductivity? Wouldn't two metal poles placed in the ground 3' > deep > and 50' apart measure a very different conductivity at night vs during > the day, > because of the daytime evaporation of surface soil water? > > Who says that the current flows deep under the ground (i.e., 1200m)? Why > doesn't > it take the path of least resistance, like current normally does (I've > never seen it do > otherwise in my entire life)? > > > > This conversation is interesting because it MIGHT eliminate the need for > a single > wire. Otherwise, it is starting to sound like the study of bumps on the > head being > related to intelligence, or mankind causing global warming with > automobiles or > cows passing gas. > > --Bob > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .