Indeed, but the crunch question is where did that data come from. We can
tell by the number 60664 that it originated probably in the 1970s.
On 2024-07-02 20:21, Ralph McDiarmid wrote:
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 zeitschriftAusg.B, 1976.
Dr. Hermstein, elektrotechnische zeitschrift Ausg. A, 1969.
These are Germanelectrotechnical 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]
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/
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]
Rick Linford at: [email protected]
For policy questions, send mail to:
Jim Bacher at: [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
<https://listserv.ieee.org/cgi-bin/wa?SUBED1=EMC-PSTC&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) <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]
Rick Linford at: [email protected]
For policy questions, send mail to:
Jim Bacher at: [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
--
Signature OOO - Own Opinions Only
Best wishes
John Woodgate, Rayleigh, Essex UK
Keep trying
--
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://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
