something like this?? In Single Wire Earth Return <http://en. ikipedia.org/wiki/Single_wire_earth_return> (SWER) AC electrical distribution systems, costs are saved by using just a single high voltage conductor for the power grid <http://en.wikipedia.org/wiki/Electrical_power_grid> , while routing the AC return current through the earth. This system is mostly used in rural areas where large earth currents will not otherwise cause hazards. A particular concern in design of electrical substations <http://en.wikipedia.org/wiki/Electrical_substation> is earth potential rise <http://en.wikipedia.org/wiki/Earth_Potential_Rise> . When very large fault currents are injected into the earth, the area around the point of injection may rise to a high potential with respect to distant points. This is due to the limited finite conductivity of the layers of soil in the earth. The gradient of the voltage (changing voltage within a distance) may be so high that two points on the ground may be at significantly different potentials, creating a hazard to anyone standing on the ground in the area. Pipes, rails, or communication wires entering a substation may see different ground potentials inside and outside the substation, creating a dangerous touch voltage.
Brian O'Connell <[email protected]> wrote: Good People, The Wisconsin Supreme Court thinks that 'stray' voltage from the power grid is causing livestock problems. Note these links to this issue. http://www.thonline.com/store/view.cfm?id=JiZNUz7AxXXkdICgz3Dz3D http://www.strayvoltage.org/stories/index.php3?Story=20010812_researchers. inc My (probably stupid) questions: 1. As most ground-loop current problems are caused when neutral is grounded at multiple points, why is the power utility blamed for an end-user wiring error ? 2. The result of 'stray' voltage would seem to be excessive ground-wire current. Why is a protection device not interrupting this fault current ? 3. The multiple instances of power distribution transformers should isolate, and therefore interrupt current leakage paths, because the customer's (secondary-side) neutral is grounded at a single point for each customer. So the only excessive (continuous) fault current should result >from the customer stringing extra grounds to the distribution transformer's case. So what is the leakage path and why is a sufficient potential developed that can cause this continuous fault current ? luck, Brian - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc - Bill You can say what you want about the South, but you never hear of anyone retiring and moving North!!! _____ Looking for last minute shopping deals? <http://us.rd.yahoo.com/evt=51734/*http //tools.search.yahoo.com/newsearch/category.php?category=shopping> Find them fast with Yahoo! Search. - ------------ --------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [email protected] For policy questions, send mail to: Jim Bacher: [email protected] David Heald: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
