Measurements of surface breakdown voltage of a creeping discharge spark air gap using POM as insulation material

Abstract

The spark gap (SG) principles for surge protective device (SPD) implementation such as gas discharge tube (GDT), have different breakdown voltage according to the applied voltage impulse steepness. Such strong steepness dependency of the breakdown voltage produces protective problems when surge and lightning overvoltage with high impulse steepness come into play. Past investigations showed that this dependency is less for creeping discharge spark gaps (CDSG). The main problem of the CDSG is the insulation surface degradation due to discharges, which also influences the breakdown voltage under stationary conditions. This issue can be solved with the use of insulation materials with low creeping discharge degradation rates such as POM (polyoxymethylene or polyacetal). Several tests were made during this work to assess the steepness dependency using POM as insulation material. Such experiments showed that the steepness dependency is less as well for POM and confirmed the suitability of this material for implementation and use in surge and lightning protective devices.