John, ----- Original Message ----- From: "John Woodgate" <j...@jmwa.demon.co.uk> > > In most countries, that technique (TN-C-S) is used only if the combined > neutral and grounded conductor is grounded at many places, so that if it > breaks, load current is distributed among the grounding points and remains > at safe values in all conductors.
Currently only 3-wire installations are made here, but I was speaking about old ones. Even if each flat had its own grounding the problem can appear between rooms, specially because there were no direct connection from main entrance point to each socket, but there were plenty connections on the way in the connection boxes under the ceiling over each socket. > Your point, effectively about SELV being preferred to PELV where the power > circuit protection is by fuses, is valid, being the lesser of two evils > (increased risk of electric shock, versus increased risk of fire, if > segregation is violated). I disagree (or I misunderstood). In my opinion in such installations SELV gives less risk of electric shock and less risk of fire. I see the question should be: How more safety PELV gives in new installations and how less in old ones. Then these coefficients should be multiplied by the ratio of new installations to old installations and at some date will be (or was been) the point when PELV becomes statistically more safety, but it is really hard to count it. Piotr Galka - 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 <emc-p...@ieee.org> 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 <emcp...@ptcnh.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
