Guest editorial: Interface charging phenomena for dielectric materials

Interface charge accumulation, leading to unpredictable insulation breakdown, restricts the development and industrialisation of high voltage direct current (HVDC) power equipment. Understanding the mechanism of interface charge transport and interface charge triggered dielectric breakdown is, therefore, of particularly high interest and vital importance. For example, the surface charging of aircraft in space brings damage to board electronic instruments as well as interference to sensing systems. Moreover, the randomly distributed charge clusters on the spacer surface, as shown in the cover page of this Special Issue, is considered as a potential threat to the surface flashover, while the accumulation of space charge within the insulating material poses a threat to the reliability of DC power cables. However, currently we still know very little about the development of charge dynamics in different interfaces, and the related breakdown mechanism of dielectrics induced by charge accumulation is also not very clear. This Special Issue brings together recent studies of charging phenomena for dielectric interfaces including vacuum-solid interface, gas-solid interface, and solid-solid interface. Nine highquality papers are accepted for publication in this Special Issue: six papers focusing on gas-solid interface (including one review paper), two review papers focusing on vacuum-solid interface, and one paper focusing on solid-solid interface. A brief discussion of each paper is presented as follows.