I've seen some interesting methods to achieve the easiest means of making an equipotential by connecting to ground, when they that are making the attempt do not understand the either concept - ground or equipotential. Imagine how far down one might have to drill and drive a ground rod in the center of a very large building that covers acres of earth providing a large dry area beneath. ps. (tongue in cheek) the ISS is grounded via its plumbing, the water pipes, and when that breaks it causes all those electrical problems.
- Bill Indecision may or may not be the problem. --- On Tue, 3/17/09, [email protected] <[email protected]> wrote: From: [email protected] <[email protected]> Subject: RE: Intersting question!! To: "'John Woodgate'" <[email protected]>, [email protected] Date: Tuesday, March 17, 2009, 2:19 PM > There is no need. There is no 'earth' inside a car. The concept or > 'earth'/'ground' is widely misunderstood. In a building, the > only reason > for 'earthing' stuff is that the electricity supply has the neutral > earthed. I disagree. From a safety perspective, the reason for earthing is to provide an equipotential environment where everything that can be touched is at the same potential. If everything is at the same potential, then no current will pass through the body, and an electric shock event is averted. Since earth/ground is commonly available, and most non-electrical appliances and other things are electrically connected to earth/ ground, the easiest means for making an equipotential environment is to connect everything to ground. (Indeed, the old U.K wiring system, TT, did just this.) If the local environment is equipotential, be it a car or a home, then we don't really care whether the supply system neutral is earthed/grounded or not. From a fire perspective, the earthing/ grounding equipotential current return path of an earthed supply system must be capable of carrying the fault current -- without overheating -- until the overcurrent device operates. Best regards, Rich - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected] <http://us.mc01g.mai .yahoo.com/mc/[email protected]> > All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ 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] <http //us.mc01g.mail.yahoo.com/mc/[email protected]> > Mike Cantwell <[email protected] <htt ://us.mc01g.mail.yahoo.com/mc/[email protected]> > For policy questions, send mail to: Jim Bacher: <[email protected] <http: /us.mc01g.mail.yahoo.com/mc/[email protected]> > David Heald: <[email protected] <http:/ us.mc01g.mail.yahoo.com/mc/[email protected]> > - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ 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]>
