Don't know about today, but the Power companies used to measure and plot ground potential rise (or fall) as electrical storms passed through an area -- perhaps worried about the differential between ground and the conducting lines?? Or maybe of bigger concern at substations ??
Haven't seen this data for some years, but perhaps to get any potential difference worth worrying about one would need to have one foot in your end zone and the other in the other guys end zone.... Michael Hopkins Thermo Fisher Scientific One Lowell Research Center Lowell, MA 01852 Tel: +1 978 275 0800 ext. 334 Fax: +1 978 275 0850 mobile: +1 603 765 3736 [email protected] From: [email protected] [mailto:[email protected]] On Behalf Of Kunde, Brian Sent: Tuesday, December 11, 2007 4:35 PM To: Tarver, Peter; John Woodgate; [email protected] Subject: RE: stray voltage ??? Thinker??? This thread makes me think of that woman who claimed that ambient electromagnet fields made her sick and gave her headaches though modern medicine could find nothing wrong with her. She ended up moving away >from the city and lined the rooms of her house with aluminum foil. When she goes outside, she wears a bee keepers hat made with wire screen to block the rf fields from getting to her brain. Is she a nut or could she just be more sensitive to EMI than the average person? It is commonly believed that animals are more sensitive to their environment, such as all the animals knew the tsunami was going to hit in Indonesia and found higher ground. Could cows sense the currents in the ground? If so, what is the difference of a cow standing on the ground with stray voltages and a bird sitting on a power line? I don't see birds complaining. LOL. Lightning Rods transfer electrons into the air to help neutralize the charge between the air and ground during electrical storms. Farmers have witnessed during storms their cows running wild in the field with plasma forming (St. Elmo's Fire) around their horns acting like a lightning rod (the cows don't like that). Could something like that be happening where a cow is the conduit for electrons passing between the ground and the air? Maybe they should make faraday cage suits for cows to protect them >from stray voltages. I wonder if there is any money in this idea? Something to think about. The Other Brian From: [email protected] [mailto:[email protected]] On Behalf Of Tarver, Peter Sent: Tuesday, December 11, 2007 2:27 PM To: John Woodgate; [email protected] Subject: RE: stray voltage ??? > From: John Woodgate > Sent: Tuesday, December 11, 2007 9:13 AM > > Tarver, Peter writes: > > >This is a part of the ELF/VLF debate, where contention is > made that HV > >power lines routed near schools and housing causes increases in the > >incidence of cancers and other illnesses, especially in children, or > >the power lines are routed near dairy cattle effecting their milk > >production. > > I disagree; these 'stray currents' are real. I have made no judgmental statements about what's real or imagined. One of the web sites mentioned in the OP was strayvoltage.org. I recognized this web site from several years ago and remember clearly that their concerns centered around the issues I mentioned above and that their concerns were primarily related to high voltage distribution, though might have included medium voltage distribution near schools. Even though a court has sided with dairy farmers, the debate will continue. > The alternating > currents in the overhead conductors have mutual inductance (not much, > but enough) with conducting (resistive) soil, and therefore voltage > gradients are induced in the soil. Cows are astonishingly sensitive to > these voltage gradients, partly because of their long 'heelbase' > (sorry!), but also due to their physiology. See IEC TS60479-3. As > little as 25 V r.m.s. > can kill a cow, and even very low voltages can put cows under enough > stress to affect milk yields and general health. These were among the points made by strayvoltage.org. Again, I made no judgment about the veracity of any claims, one way or the other in the above. > >On-premise protection devices do not come into play and > grounded supply > >conductors do not exist, because primary distribution is > >three-phase-delta. > > I don't know what happens in USA, but in UK all line towers are > connected together by an overhead grounded conductor at the top of > each tower. To what extent this affects ground currents under normal > conditions is questionable, but it does complete a big loop: tower - > conductor - tower - ground ---- ground - tower. And if there is a > loop, some current is bound to flow at some time. Grounded supply conductor = Neutral. I don't pretend to know every reason for running these groundING wires between towers, but I understood they provide lightning protection by presenting lightning with a preferential path to ground, rather than through the phase conductors. Regards, Peter L. 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