Flashover characteristics of polypropylene films in SF6 using nanosecond pulses

Abstract

The surface flashover characteristics of BOPP (biaxial-oriented polypropylene) films in SF 6 under nanosecond-pulsed voltages are experimentally investigated in this research by using finger electrodes and using the front-edge flashover method. The test factors include the gas pressure, electrode distance, pulse voltage steepness, pulse polarity and applied field direction. The flashover voltage first increases with gas pressure and then saturates at a certain value, such as 0.4 MPa for a 9 mm gap. The more serious the field distortion is, the lower the saturation gas pressure. The increase in the pulse voltage steepness enhances the flashover voltage in general, but a frap phenomenon of the flashover voltage occurs, and the flashover voltages under pulses with steeper fronts are lower at some pressures. Generally, the negative flashover voltage is higher than a positive voltage by using finger-cuboid electrodes, especially at high pressures. The flashover voltage on the film surface with a normal electrical field component is higher than that with a parallel component at low pressures and lower at high pressures. Moreover, a qualitative avalanche model based on the accumulation and emission of surface charges on the films and the field distortion effect of space charge behaviors is employed to explain the above experimental results.