The shielding layer leads a wire to be grounded, which is the reference point of potential. Conventional shielding is done between the primary and secondary windings. Whether it is the outermost layer or the inner winding shielding, you need to pay attention: when the winding is wrapped with copper foil, the copper foil overlaps the ends of the copper foil and needs to be insulated. The reason is simple: if there is no insulation, overlapping and connecting is a short-circuited coil!
