Characteristics of Nanosecond Pulse Dielectric Surface Flashover in High Pressure SF6

Surface electrical insulation performance is an important issue in pulse power devices. In order to investigate the surface flashover characteristics in an environment of high pressure SF6, a flashover experiment platform was established with nanosecond pulse voltage supply. The flashover characteristics of polymethylmethacrylate (PMMA) specimens with circular truncated cone shapes were subsequently determined under incremental SF6 pressures from 0.2 to 1.0 MPa. As the angle of cone increased, the flashover voltage (FV) rose under low pressure condition, but fell at first and then rose at high pressure. The surface length and the field nonuniform factor were the main influences of FV with angle. In addition, the FV rose linearly at first and then reached its maximum when gas pressure increased, and it was easier to reach the maximum when the field nonuniform factor was higher. A high speed camera was also applied to get the photos at different period of flashover, and the luminous processes of flashover along different specimens were discussed in particle perspective.