THE United States Navy operates antennas on the Very Low and Low Frequency (LF) bands (10 to 300 kHz) for long range communication. These antennas operate at voltages above 200 kV and in a variety of locations ranging from tropical to frigid climates. Consequently, there is interest in their performance under a wide variety of environmental conditions. The interest stems from the fact that insulation equipment that was designed and tested at power frequency (50/60 Hz) did not operate as expected when used at VLF/LF [1, 2]. In several cases catastrophic failure of insulated support structures due to the arc produced by the external breakdown of the device have occurred [1]. To improve equipment design and reliability, there is a need to understand the breakdown processes involved.