Charge dynamics: Linking traps to insulation failure

The transport of the available charge carriers is a key issue to determine the macroscopic behaviors of insulating materials. Although the rapid developments of experimental and numerical techniques make great contributions to the understanding of the space charge dynamics, the charge carrier mobility and the nature of traps in various situations of electric field and temperature in polymeric materials, the relationship between the insulation failure and the charge transport still remains unclear. As a result, the way continues to further understand the links, particularly in the view of traps. This paper indeed focuses on these significant links and describes the effective methods to improve insulation properties based on the links. The short-term insulation failure including the breakdown and surface flashover, and the significant methods such as employment of nanostructured fillers and surface treatments of polymers, are discussed. Considering the characteristics of charge capture, the effect of trap filling and the numerical techniques with high precision, the charge transport behaviors in polymers are investigated based on surface potential decay (SPD) and bipolar charge transport (BCT) models. The deep trap can effectively reduce carrier mean free path and the energy obtained from applied field. Consequently, the breakdown strength increases as an increase of deep trap. The deep trap can effectively reduce charge mobility and then the conductivity. The trap sites, especially for deep traps, can be modified by employing nanostructured fillers and surface treatments. These modifications can influence the charge injection, the impact ionization within the low-density regions, and the flashover development processes. In this way, electrical breakdown strength and surface flashover performance are improved.