A classic reference. We have a copy in our library here. The only time I’ve seen trace-trace breakdown was on a PV combiner circuit board, where the creepage distance was about ¼ of what was called out by the standard. The resulting failure was repeatable using impulse voltage withstand testing, which suggested that it was a clearance failure rather than creepage. The board was not conformal coated, although there was solder mask.
I’ve long assumed that creepage distance requirements in 60664 have lots of margin built in. Pollution degree microenvironments are defined in a way which makes distinction a little vague. Pollution degree 2 Only non-conductive pollution occurs except that occasionally a temporary conductivity caused by condensation is to be expected Pollution degree 3 Conductive pollution occurs or dry non-conductive pollution occurs which becomes conductive due to condensation which is to be expected. PD2 likely a suitable assumption for any used at home, at an office, a classroom, a retail store in mall, or in a well air-conditioned building. However, I wouldn't expect condensation in those environments. PD3 likely a suitable assumption for equipment in a garage, a shed, a workshop, or inside buildings which are neither air-conditioned nor heated, or in bathrooms, change rooms and the like. Accumulation on surface of the PCBs and on components could be conductive when dry. (e.g. soot or carbon dust) And, condensation would be expected. Ralph McDiarmid Product Compliance Engineering Solar Business Schneider Electric From: Richard Nute [mailto:ri...@ieee.org] Sent: Wednesday, May 17, 2017 10:53 AM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] low voltage insulation coordination With the help of Dan Roman (thanks!), the research into clearance and creepage distance by Klaus Stimper, "The physical fundamentals of LOW-VOLTAGE INSULATION CO-ORDINATION" is now available at: http://www.ieee-pses.org/Downloads/low_voltage_insulation_coordination.pdf This classic research is the basis for IEC 664 and IEC 60664-1 standards. If you have ever wondered why our spacings are what they are, this treatise is for you. Enjoy. 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 <emc-p...@ieee.org> 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://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
