Analysis of Influence Factors on AC Breakdown Characteristics of Rod-Barrier Gap and Electric Field Simulation

The insulation performance of air gap can be improved by inserting insulation barriers into the high voltage box with limited space. The influence of the barrier dimension, barrier thickness, barrier position and surface state of epoxy resin barrier on the AC breakdown characteristics of the “rod electrode-insulation barrier-ground electrode” system are discussed in the work. An equal-size model of the insulation system is established to analyze the influence of the insulation barrier on electric field and the discharge mechanism. The experimental results indicate that the breakdown voltage is improved significantly by enlarging the barrier dimension, up to twice as much. In contrast, the barrier thickness has little effect on the breakdown voltage because the discharge is mainly along the barrier surface. Besides, the breakdown voltage can be increased by reducing the distance between insulation barrier and rod electrode, this is because of the blocking effect of insulation barrier on the corona layer around the electrode, which can hinder the development of charges to the ground electrode, thus delaying the discharge process. The breakdown voltage increases with the barrier surface roughness because of the prolongation of discharge path and the distortion of local electric field. The breakdown voltage decreases with the rise of temperature, it decreases to 37.5 kV when temperature rose to 60 °C. Due to the increase of free charges mobility, the corresponding surface resistivity decreases from 16.2 × 10 14 Ω at 20 °C to 3.14 × 10 14 Ω at 60 °C. This work can provide support for the reasonable design of insulation barriers in engineering application.