I'm aware of IEC 60664-1 (insulation coordination) and I've referenced it many times over the years. You'll find its normative reference in several IEC and CSA standards and UL840 seems to rely on its database. IEC 60664 has been around a long time and has several parts.
Ralph From: Richard Nute <[email protected]> Sent: Friday, June 28, 2024 3:31 PM To: [email protected] Subject: [PSES] dielectric strength question -- update Since my 23 June message, I may have found the answer to my quest as to where the air insulation (clearances) distances came from: IEC 664, Edition 1, 1980, Appendix Table AI, withstand voltages, and Table AII, breakdown voltages. According to IEC 664, Table AII is "experimental data" by Prof. Dr. Ing. W. Pfeiffer, convenor of IEC TC109/MT3, elektrotechnische zeitschrift Ausg. B, 1976. Dr. Hermstein, elektrotechnische zeitschrift Ausg. A, 1969. These are German electrotechnical journals issue A, 1969, and issue B, 1976. I could not find copies of these. Perhaps our German subscribers can find these. I surmise from the tables that these two people tested air breakdown voltage as a function of distance. I did find that Dr. Hermstein did some experimental work on electrical performance of gasses that has been discredited. Table AI (IEC 664) is withstand voltages based on the breakdown voltages in Table AII (IEC 664). This is the source of IEC 60664-1 clearance distance tables which have been used by a number of IEC standards committees. I've attached a plot of both the breakdown voltage per distance and the withstand voltage per distance through air. These are linear axes while the IEC 664 and IEC 60664-1 plots are logarithmic axes. I've included trend lines (dotted) and their equations. (The voltage-distance tables are not in IEC 60664-1.) I suspect the non-linearity of the breakdown (red) line is due to measurement problems. I would expect the line to be straight except for the small dimensions that approach the Paschen voltage limit for air, 327 volts peak. (Paschen studied gas breakdowns at very small gaps and found that various gasses do not break down at very small gap dimensions.) 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 [email protected] <mailto:[email protected]> All emc-pstc postings are archived and searchable on the web at: https://www.mail-archive.com/[email protected]/ <https://www.mail-archive.com/[email protected]/%20> Website: https://ewh.ieee.org/soc/pses/ <https://ewh.ieee.org/soc/pses/> Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) <https://ewh.ieee.org/soc/pses/list.html> List rules: https://ewh.ieee.org/soc/pses/listrules.html For help, send mail to the list administrators: Mike Sherman at: [email protected] <mailto:[email protected]> Rick Linford at: [email protected] <mailto:[email protected]> For policy questions, send mail to: Jim Bacher at: [email protected] <mailto:[email protected]> _____ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC <https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1> &A=1 - ---------------------------------------------------------------- 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: https://www.mail-archive.com/[email protected]/ Website: https://ewh.ieee.org/soc/pses/ Instructions: https://ewh.ieee.org/soc/pses/list.html (including how to unsubscribe) List rules: https://ewh.ieee.org/soc/pses/listrules.html For help, send mail to the list administrators: Mike Sherman at: [email protected] Rick Linford at: [email protected] For policy questions, send mail to: Jim Bacher: <[email protected]> _________________________________________________ To unsubscribe from the EMC-PSTC list, click the following link: https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&A=1
