>What voltages can I expect on the Neutral (referenced to ground) line in various countries >and connection systems? Is there a limit on how high the voltage may be, both in normal and >fault conditions?
Moshe, THE's booklet, "World Electricity Supplies", lists the supply voltage, frequency, and power distribution systems used in over 200 countries. You can order it through Technical Standards Services, Ltd. webpage at http://www.techstandards.co.uk/thsguide.html "TN" and "TT" power systems (IEC 950 1.2.12.1 and 1.2.12.2) are the ones usually encountered. Neutral-to-ground voltages should be less than a few (5 or so) volts even under a line-to-ground fault. Hospitals and other high-reliability installations sometimes use "IT" power systems (IEC 950 1.2.12.3) permitting continued operation even if a line-to-ground fault occurs-- at the cost of: * Neutral-to-ground voltage approaching the single-phase line voltage. * In a three-phase system, the other phase-to-ground voltages approaching sqrt(3) times the single-phase line voltage. This can double the required creepage and clearance distances for (to us) a tiny additional market. So we specify that our products are not to be installed on IT power systems, but may be powered by an isolation transformer that gets its power from an IT power system to create a local TN-S power system. John Barnes Advisory Engineer Lexmark International --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, jim_bac...@monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).
