Effects of non‐linear conductivity on charge trapping and de‐trapping behaviours in epoxy/SiC composites under DC stress

Abstract

Gas‐insulated switchgear (GIS) spacers are made of epoxy resin. However, the surface charge accumulation has been a great concern to the safe operation of GIS, which causes the frequent flashover faults on spacers. In this study, micro‐silicon carbide (SiC) particles with non‐linear conductivity were added into epoxy matrix and the filler content varied from 0 to 14 vol%. Then, the bulk conductivity and surface potential decay (SPD) tests were conducted. The obtained results showed that the epoxy/SiC composites have obvious non‐linear conductivities and the non‐linear‐conductivity threshold decreases with the increasing filler content. The addition of SiC can effectively resist the rise of surface potential and enhance the surface charge dissipation process. From the trap energy distributions, it can be inferred that the deep traps of ∼0.9 eV should be the intrinsic traps of epoxy and the shallow traps of ∼0.8 eV are considered to be introduced by SiC. Furthermore, the simulation results confirmed that the sharp increase of carrier mobility in non‐linear region significantly reduces the remaining time and possibility of a de‐trapped charge being recaptured by traps before reaching the grounded electrode. Therefore, the high conductivity in non‐linear region contributes a lot to the increase of SPD rate.