The code leaves such isolation practices up to the product standards such as those for electronic equipment, switchgear, devices, wire, etc. It primarily covers lightning protection by requiring grounding of separately derived services and other exposures like antennas. It does not seem to get into insulation specification or ratings within the code. Lightning protection is best provided by a process called insulation coordination, where a planned breakdown path is provided through gaps, breakdown devices, and such so that neighboring insulation bypassed and not destroyed. Generally you are protecting against induced voltages, not direct strikes. Direct strike protection is provided by the standards for lightning rods and systems. IEEE, IEC and the telecom industry have made various studies of transients typical of power and comm circuits which have been used to establish spacings and insulation within product standards.
Bob Johnson ITE Safety <http://www.itesafety.com> Grasso, Charles wrote: Hi folks – I have a bit off the wall question for you. The NEC code requires grounding to protect the consumer against lightning induced effects: Q. How much isolation would be required between the lightning-energized external hardware and the internals of electronic equipment to provide the equivalent protect if the external hardware were (for some reason) ungrounded? Best Regards Charles Grasso Compliance Engineer Echostar Communications Corp. Tel: 303-706-5467 Fax: 303-799-6222 Cell: 303-204-2974 Pager/Short Message: [email protected] <BLOCKED::mailto:[email protected]> Email: [email protected] - ---------------------------------------------------------------- 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 ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please visit http://www.messagelabs.com/email ______________________________________________________________________ - ---------------------------------------------------------------- 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
