Hi, Rich. I thought you were writing about solid dielectrics. I did a
Google search for the German journal and it seems that its issues may be
available up to 1995. The organization VDE should be able to help you:
https://www.vde.com/en. Also, the search turned up a book that seems to
have relevant information, at
https://www.google.co.uk/books/edition/Electrical_Properties_of_Solid_Insulatin/c9qgPOK7eNwC?hl=en&gbpv=1&dq=elektrotechnische+zeitschrift&pg=PA220&printsec=frontcover
On 2024-06-28 23:31, Richard Nute wrote:
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 journalsissue 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
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Best wishes
John Woodgate, Rayleigh, Essex UK
Keep trying
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