A high-voltage insulator has at least two separate insulators that can be joined to create a post and that each have an essentially rotation-symmetrical support tube made of glass-fiber-reinforced epoxy resin and having an empty internal space, respective top and bottom metallic flanges that surround top and bottom ends of the respective support tube and close the respective tube's empty internal space with an air-tight seal relative to the outer atmosphere, and a shielding of silicone that fits around each support tube. A tubular coupling piece connects the at least two insulators in such a way that the respective empty internal spaces of the at least two insulators form a common gas space and pressure between the spaces is equalized through the coupling piece.