Influence of Metal Particles on Surface Charge Accumulation Characteristics of Spacer in SF 6 /N 2 Mixtures under Impulse Voltage

When metal particle is attached on the surface of spacer, it will affect the surface charge accumulation and electric field, and reduce the surface insulating level of insulators. Therefore, it is important to research the relationship between attachment of metal particle and surface charge accumulation. In this paper, the influence of metal particle on surface charge accumulation characteristics of spacer in 5atm 20 % SF 6 /N 2 is researched. In the experiment, a cylindrical copper wire of 0.5mm diameter and variable length is fixed on the surface of a downsized truncated cone-type spacer, and one end of this wire is in contact with the high voltage electrode. A lightning impulse voltage with different amplitudes is applied to the central electrode for 5 times, then the surface potential of spacer is measured by a Kelvin vibrating electrostatic probe, and the corresponding surface charge density is further calculated by a reversed algorithm. The results reveal under lightning impulse voltage there are just bipolar charges around the metal particles and random charges existing. When the metal particle is over 5mm, a randomly distributed charge will result in a decrease in the amount of accumulated charge near the metal particles. In addition, the amount of bipolar charge accumulated near the metal particles increases with the increase of the applied voltage amplitude, and the accumulating range of the homo-charges at the ends of the metal particles increases as the applied voltage amplitude increases.