A method of manufacturing a capacitive electrical device is disclosed. The method includes a) bonding a first electrical insulation film with a second electrical insulation film to obtain a single electrical insulation film that has a larger surface area than any of the first electrical insulation film and the second electrical insulation film has alone, b) providing a conductive layer onto the single electrical insulation film, and c) winding the single electrical insulation film and the conductive layer around a shaft to obtain a layer of the single electrical insulation film and a layer of the conductive layer wound onto the shaft, thereby forming the capacitive electrical device.