The effect of relative humidity on the flashover strength of solid insulation

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This paper informs on the flashover strength of 3 materials: Delrin (Polyoxymethylene), HDPE (High Density Polyethylene) and Ultem (Polyetherimide) with 'smooth' and 'knurled' surface finishes, in zero-grade air at -0.5, 0 and 0.5 bar gauge, and at <; 10%, ~50% and >90% relative humidity (RH). All tests were completed using a 10-stage Marx generator, producing HV impulses with a nominal 100/700 ns waveshape. Each test conformed with the ASTM D3426-97 standard of 'step up' testing, to find the average flashover voltage for each set of conditions. The electrode system with each dielectric material demonstrated a decrease in breakdown voltage as the RH was increased. In high humidity environments, the knurled surface finish was seen to have a positive effect on the flashover strength of Delrin and Ultem samples, compared to a smooth, machined surface. Increasing pressure yielded an increase in the flashover strength also. For samples with a smooth surface finish, a decrease in flashover strength was found as the permittivity of the material increased, irrespective of humidity and pressure. However, a knurled surface finish had a much more erratic effect on flashover strength, with no discernible trend with increasing material permittivity
Original languageEnglish
Title of host publication2019 IEEE Pulsed Power & Plasma Science (PPPS)
Place of PublicationNew York
Number of pages4
ISBN (Electronic)9781538679692
ISBN (Print)9781538679708
Publication statusPublished - 27 Feb 2020
Event2019 IEEE Pulsed Power and Plasma Science - Orlando, United States
Duration: 23 Jun 201929 Jun 2019

Publication series

NameIEEE Pulsed Power Conference
ISSN (Print)2158-4915
ISSN (Electronic)2158-4923


Conference2019 IEEE Pulsed Power and Plasma Science
Abbreviated titlePPPS 2019
Country/TerritoryUnited States
Internet address


  • flashover
  • dielectric
  • gas breakdown
  • air
  • humidity
  • humidity control
  • impulse breakdown
  • high voltage
  • flashover voltage
  • discharge voltage
  • electric discharges
  • insulation
  • insulation materials
  • insulation testing
  • insulation systems
  • pulsed power
  • pulsed power technology


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