Influence of Impregnation State on the Electrical Characteristics of Polypropylene Film for High-voltage capacitors

Biaxially oriented polypropylene (BOPP) film are generally impregnated in benzyltoluene, which constitute insulating medium of high-voltage capacitors. In order to investigate the electrical properties of impregnated film, this paper builds a test platform for the electrical properties of polypropylene film, and selects key electrical properties such as relative dielectric constant, dielectric loss and breakdown field strength. Testing five thicknesses of film to obtain the laws of the influence of impregnation state on electrical parameters at different temperatures and field strengths. The test result shows that: 1) Dielectric constant of the impregnated film increases from 2.25 to 2.27 at room temperature, the dielectric loss increases from 1.39×10 ^-4 to 2.7×10 ^-4 , the average value of DC breakdown field strength of the 13 μm film increases from 619 MV/m to 683 MV/m, the average value of AC breakdown field strength increases from 420 to 460 MV/m. 2) Impregnated film is more affected by the temperature and field strength. The temperature changes from 293K to 353K, the growth rate of dielectric constant increases from 0.5% to 2% after impregnation, and the dielectric loss increases from 1 to 1.5 times. 3) Breakdown field strength increases and then decreases with the thickness, and 13μm film has the highest breakdown field strength.