Particle Expelling and Discharge Suppression by Permittivity Gradient Design of AC-GIS Spacer

The presence of metal particles is responsible for the unpredictable flashover faults of spacers in gas insulated switchgears (GIS). In this study, an innovative method is put forward to actively expel metal particles by utilizing the permittivity functionally graded material (ε-FGM) spacer. Based on an 800 kV GIS model, the electric field distribution and the metal particle motion around the spacers are studied by numerical simulation. Then, the particle motion and the flashover tests are both conducted based on two downsized samples of the uniform and the ε-FGM spacers. Results show that the maximum electric field is located at the triple junction of the uniform spacer, and the metal particles tend to jump towards the spacer under Coulomb force, reducing the flashover voltage by up to 12%. By applying the ε-FGM spacer, the electric field at the triple junction is decreased by 26.2%, improving the flashover voltage by 11.5%. Meanwhile, the bending orientation of electric field lines surrounding the ε-FGM spacer is changed, causing an opposite Coulomb force compared to the uniform spacer in the axial orientation. Therefore, metal particles released nearby are expelled away from the ε-FGM spacer, and the corresponding flashover voltages are almost the same as that in the case of none particle.