Thank you Richard :)
All the best James From: Richard Nute <[email protected]> Sent: 01 October 2026 19:31 To: [email protected] Subject: Re: [PSES] Spacings Hi James: I need to point out three safety standard conditions for CTI: 1. CTI is an insulation parameter for basic, supplementary, and reinforced organic insulations. If using IEC 62368, CTI only applies to ES3 voltage circuits. (For reliability, you may want to apply CTI to other circuits.) 2. CTI applies only when the surface of solid organic insulation (between two conductors) is subject to contamination. 3. CTI voltage parameter is steady-state voltage (across the insulation) and related “creepage” distance requirements; hi-pot voltage is not applicable. In answer to your question: Is this a measure of the pyrolysis characteristics of the material? Yes. IEC 60112 determines the CTI rating of a material based on the withstand voltage during and after 50 drops of NH4Cl-solution. (Pyrolysis is a process involving the separation of covalent bonds in organic matter by thermal decomposition within an inert environment without oxygen. Wikipedia.) Best regards, Richard Nute Bend, Oregon, USA [email protected] <mailto:[email protected]> From: James Pawson (U3C) <[email protected] <mailto:[email protected]> > Sent: Wednesday, September 30, 2026 12:46 AM To: [email protected] <mailto:[email protected]> Subject: Re: [PSES] Spacings Hello Richard, Thank you for the interesting background, it helps with my understanding of the “why” 😊 Where does the Comparative Tracking Index (CTI) of the material come into play? Is this a measure of the pyrolysis characteristics of the material i.e. how easily the non-insulating components of the insulating material can be separated and turned into conductive materials? Or is there another force at work? Thanks and all the best James ( <https://www.ggtemc.co.uk/esd/> shameless plug for my new book) James Pawson Managing Director & EMC Problem Solver Unit 3 Compliance Ltd EMC : Environmental & Vibration : Electrical Safety : CE & UKCA : Consultancy <http://www.unit3compliance.co.uk/> www.unit3compliance.co.uk | <mailto:[email protected]> [email protected] +44(0)1274 911747 | +44(0)7811 139957 2 Wellington Business Park, New Lane, Bradford, BD4 8AL Registered in England and Wales # 10574298 _____ 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://pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf 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 email has been checked for viruses by AVG antivirus software. www.avg.com - ---------------------------------------------------------------- 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://pses.ieee.org/wp-content/uploads/2024/12/EM-PSTC-List-Rules.pdf 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
