Gert, I have a tutorial somewhere that speaks of the relationship of CTI, pollution, and the presence of humidity as contributing factors to the breakdown of insulating surfaces. A study of the tracking mechanism is required and when voltage is applied, how the material is carbonized by micro discharges and partial discharge to form conductive trenches on the surface on a microscopic scale. I too have seen the mentioned papers, and they do not adequately go into this topic. The Klaus Stimper book is helpful, I have a copy.
I also found http://books.google.com/books/about/High_voltage_technology.html?id=cOpSAAAAMAAJ an excellent resource. Most books that do a good job presenting this material are no longer in print. For many professionals in High Voltage Design, this is considered the premier reference. The breakdown mechanism for surfaces, solids and gases is different in each case. When these insulating systems are adjacent, there is some influence. I find the safety standards and even 60664-1 an incomplete tutorial on the subject. And to be fair this is not their main purpose. Thanks, - doug Douglas Powell http://www.linkedin.com/in/dougp01 Original Message From: ce-test, qualified testing bv - Gert Gremmen Sent: Tuesday, May 13, 2014 3:58 AM To: [email protected] Reply To: ce-test, qualified testing bv - Gert Gremmen Subject: Re: [PSES] Creepage and RMS The analogy I made with a battery was (very) loose, strictly spoken it's average current not rms current. I wanted to emphasize that chemical reactions do not suddenly happen on the arrival of a electrical field, but need time to process in a similar way a battery is not fully charged on the connection of a voltage on its terminals. Apparently the committee writing IEC 60664 found the application of RMS more suitable then using an average (=voltage integrated over time). Rich wrote that the process of deterioration is of a dissipative nature and power related. Of course, more volt, more power, so that relation is clear. I wonder if that relation (deterioration = dissipation) is as strict as that (I mean dissipative) given the number of processes that seem to happen at the boundary of (polluted) air and insulator. But as the majority seem to be electrochemical I am not surprised that the effects are better measured using RMS (or average) value than a peak value. I have been trying to find the paper mentioned (from Klaus Stimper) before but was not successful. I wonder if that would shine some light on the subject. Is there someone that can forward me a copy ? I have been checking creepage for years based on the same voltage as clearance, just because the standard did not mention the difference clearly. (It has never been a problem either as most products were largely over-insulated). Ther fore I want to ask anyone on this list involved in safety standardization to bring this to their committee: that standards should emphasize this aspect (peak for clearance, rms for creepage) in one of the first paragraphs on insulation, as currently this is more or less hidden in the tables only. A good working definition of working voltage and a simple indication on how to measure that (in respect to insulations) would also help. Regards, Ing. Gert Gremmen, BSc -----Oorspronkelijk bericht----- Van: John Woodgate [mailto:[email protected]] Verzonden: Tuesday, May 13, 2014 11:25 AM Aan: [email protected] Onderwerp: Re: [PSES] Creepage and RMS In message <[email protected]>, dated Tue, 13 May 2014, Anthony Thomson <[email protected]> writes: >If Gert means 'charge' in the number of Coulombs flowing, then the RMS >value holds. How do you arrive at that conclusion? -- OOO - Own Opinions Only. With best wishes. See www.jmwa.demon.co.uk Nondum ex silvis sumus John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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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://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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]> - ---------------------------------------------------------------- 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://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 <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
