X-Ray Radiation as a Possible Approach for Realizing Surface Charge Decay on Post Insulators inside SF6

Surface charge accumulation has been a long-existed issue hindering the development of insulators in gas-insulated equipment. However, the mechanism is still not clear. In this paper, the surface potential distribution before and after X-ray irradiation is analyzed, and a surface charge transport model is established. The effects of the generation rate of ion pairs and the applied voltage on the surface charge are studied. The results show that a large number of positive charges accumulate on the insulator surface after X-ray radiation. Surface charges cannot be dissipated by X-rays under online condition. Under offline condition, the conduction current in gas becomes the dominate pathway of surface charge dissipation. Since X-rays can promote the ionization of SF
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, the charged particles generated by the ionization recombine with the hetero-polar surface charges. Therefore, the surface charge can be dissipated quickly. Under the applied voltage, ions of opposite polarity in gas migrate to the insulator surface. As a result, positive charges accumulate on the spacer surface. To conclude, X-rays are only suggested as a tool for surface charge dissipation under offline operation.