AC Surface Flashover Characteristics at the Clear Edge of Metallized Polypropylene Film Capacitors

Abstract

Surface flashover significantly affects the insulation performance of metallized film capacitors (MFCs), and the clear edge is the main area where the surface flashover occurs. An experimental platform is built to study ac surface flashover at the clear edge of metallized polypropylene film capacitors. The effects of interlayer pressure, experiment temperature, clear edge width, square resistance, absolute humidity, and voltage frequency on the ac surface flashover of metallized films are investigated. The results indicate that the surface flashover voltage and field strength increase with the increase of interlayer pressure in the range of 100–800 kPa and decrease with the increase of experiment temperature in the range of $30~^{\circ }$ C– $90~^{\circ }$ C; the flashover field strength decreases by 44% and gradually tends to be stable as the clear edge width varies from 0.5 to 2.5 mm; the surface flashover voltage and field strength increase by 78% as the square resistance increases from 7.5 to $50~\Omega $ / $\Box $ ; the surface flashover voltage increases with the increase of absolute humidity in the range of 4–16 g/m3; the surface flashover voltage and field strength decrease by 4% with the increase of voltage frequency in the range of 50–400 Hz. In the design and manufacture of MFCs, the interlayer pressure of outer films should be appropriately increased; the design of the clear edge width of MFCs with different square resistance, operating temperatures, and voltage frequencies can be selected according to the experimental results of this article. Since the moisture will be removed by heating and vacuumizing in the capacitor manufacturing process, the design of the clear edge width could refer to the experimental results under low humidity.