HV standoff distance

[David Lesher]

Someone has tried to tell me that the free-air distance needed
to prevent arcing varies inversely with frequency; i.e. a 10 KV
RMS 60Hz conductor will need less spacing than a 10 KV RMS 25Hz
one.

I'm no power distribution engineer, but I can't recall anything
close to that. I asked my MIT-grad friend as well, but outside
of the obvious end case [0 Hz, where peak=RMS] we both came up
blank.

Obviously, OAT, %RH, etc alter the result, but frequency?

 

[David Lesher]

Unlike DC or 50/60 Hz AC, gap breakdown voltage for low frequency high
voltage at LF and VLF frequencies may be only slightly higher than
corona onset voltage.
....
An excellent paper covering low frequency RF breakdown can be found in
the massive study, "VLF/LF High-Voltage Design and Testing", Technical
Report 1904, Sept 2003 on the DTIC site:

http://www.dtic.mil/dtic/tr/fulltext/u2/a526052.pdf

Thanks. Reading now, but I should have been more explicit...I'm
talking DC-100Hz, not RF.

 

[Cydrome Leader]

Someone has tried to tell me that the free-air distance needed
to prevent arcing varies inversely with frequency; i.e. a 10 KV
RMS 60Hz conductor will need less spacing than a 10 KV RMS 25Hz
one.

I'm no power distribution engineer, but I can't recall anything
close to that. I asked my MIT-grad friend as well, but outside
of the obvious end case [0 Hz, where peak=RMS] we both came up
blank.

Obviously, OAT, %RH, etc alter the result, but frequency?

geometry of the conductors will make a difference too. You will get more
corona discharge and breakdown between two sharp points than the two
spheres the same distance apart.