Surface potential characteristics of polymeric barriers for a hybrid gas-solid insulation

The effect of barrier material on AC breakdown voltages of a hybrid gas-solid insulation was investigated by examining behavior of electrostatic potential on barrier surfaces. Breakdown characteristics of air insulated gaps with the barriers made of three different polymeric materials were experimentally investigated. Further, measurements of surface potential on the barriers were performed and the results were utilized for obtaining surface charge dynamic characteristics for the three polymeric materials and extracting their electric conductivities, charge carrier mobilities and trap energy distributions. It was found that the material with the lowest initial surface potential and the fastest decay rate exhibited the highest bulk conductivity and carriers' mobility as well as the lowest trap energy level. These properties provided the highest increase on the AC breakdown voltages compared with pure air. It was concluded that materials, where accumulation of charges in the bulk is inhibited and decay of surface charges is facilitated, allow for higher operating voltages of AC hybrid gas-solid insulation systems. The mechanism of the effect of barrier material on AC breakdown voltage is discussed.