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?
Hi David,
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 RF corona is hot, and the surrounding heated air becomes less dense, reducing breakdown voltage in the remaining gap. Streamers develop and quickly grow to bridge the gap. Under appropriate conditions, a pulsed source of a couple hundred thousand volts will jump a distance of 5-6 feet (i.e., as in medium sized Tesla Coils).
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:
Bert
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Thanks. Reading now, but I should have been more explicit...I'm talking DC-100Hz, not RF.
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.
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