Insulation Performance of Dielectric-Coated Electrodes in Sulphur Hexafluoride Gas

The results of a series of experiments performed in sulphur hexafluoride gas for pressures up to 100 psig (0.68 MN/m2) are described. Uniform field electrodes and both dc and standard impulse voltages were used. The volume resistivity of the dielectric material used was considered to be a significant parameter, and for this reason some graphite loaded coatings were Also used. The results indicate that the breakdown voltages were lowered by graphite loading of the material. Prebreakdown currents, not unexpectedly, were lower for higher resistivity coatings. In some cases the withstand voltage was more than three times that for uncoated electrodes. Small sized particulate contamination did not seriously affect the voltage withstand. Considerable surface charging of the coating was also observed in many cases.