Flashover of smooth and knurled dielectric surfaces in dry air

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In pulsed power engineering, solid spacers are used to insulate high voltage parts from extraneous metal parts, providing electrical insulation as well as mechanical support. The breakdown/flashover voltage, at which a discharge process initiates across the solid/air interface, is important in the design process, as it informs designers of specific threshold ‘failure’ voltages of the insulation system. In this paper, a method to potentially increase the failure voltage, tested under multiple environmental conditions, without increasing the length of the solid spacer, was investigated. Three dielectric materials: HDPE (high-density polyethylene), Ultem (polyetherimide) and Delrin (polyoxymethylene), were tested under a 100/700 ns impulse voltage. Cylindrical spacers made of these materials were located in the centre of a plane-parallel electrode arrangement in air, which provided a quasi-uniform electric field distribution. Breakdown tests were performed in a sealed container at air pressures of -0.5, 0 and 0.5 bar gauge, with a relative humidity (RH) level of
Original languageEnglish
Number of pages8
JournalIEEE Transactions on Dielectrics and Electrical Insulation
Publication statusAccepted/In press - 11 Sept 2023


  • dielectrics
  • electrodes
  • flashover
  • gas ansulation
  • high voltage
  • impulse testing
  • insulation testing
  • knurled insulation
  • nano-second Impulse
  • profiled insulation
  • pulsed power
  • rough surfaces
  • solids
  • surface modification
  • surface roughness
  • surface treatment


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