Power Distribution Gear at the low voltage load side is typically 277VL:N and 480VL:L. I am talking specifically about panel, switch gear, motor control centers, Transfer switches etc.
Why is the control wiring in these applications often specified in these applications at 600V, wouldn't 300V be adequate? Note that the control wiring is forced to stay clear of the power cabling. My thinking is that the L:N =~ L:G voltage rating should be the driving issue here. One of my co-workers found some reference that tied wire protection to the voltage rating. That if it took longer to clear long delay type faults then the voltage rating had to be increased by a proportional amount. Another reality could be some tie to ungrounded power systems and a fault to ground condition that would then rise the other lines to the L:L voltage = 480V. Similar would be a Line to Neutral fault that could push the other L:N voltage to 480 till the fault clears. All of this becomes rather important when trying to use communication cables in distribution gear. The NEC understands CM 300V cables where the conductors are power/voltage limited and the rating is more for the sheath. It does not have a similar CM+ 600V rating. The majority of the control wire bundles in the gear are 600V and so by association the coms cables need to be too. The gear does not have nice portioned areas for coms typically. As a result we play around with other NEC ratings to get 600V where the power/voltage limitation is not recognized like TC and the cables are big. For example serial asynch RS485 Modbus RTU to a meter, Belden has a 3074F I believe that is 600V TC rated and is pricey and the size of my index finger.... Your thoughts? Chris Wells Eaton Corp. - ---------------------------------------------------------------- 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.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. 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]>
