An insulator for electrically insulating an electrical conductor. The insulator includes a roll defining a central longitudinal through hole along a longitudinal axis of the insulator. The through hole is arranged for allowing an electrical conductor to pass there through. The insulator also includes at least one shed arranged on an outer surface of the roll. The shed includes a shed tip having an outer non-flat curvature defined by a plurality of different radii of curvature and including a most distal point of the shed. An end radius of curvature at the most distal point of the curvature is larger than a first radius of curvature at one side of the most distal point and a second radius of curvature at the other side of the most distal point.

An interface breakdown-proof locomotive roof composite insulator. The composite insulator comprises: a support body; and at least five shed groups arranged side by side along the axial direction that are provided around the sidewall of the support body, the at least five shed groups includes: at least four shed groups located on the upper end with each group including a large shed and a small shed; and at least one shed group located on the undermost end with each group including two small sheds. For such a shed structure, it is favorable to tolerate impulse voltage, and it is difficult for the interface to be broken down; the electric field on the interface even does not exceed 3 kV/mm, and even if a gas exists on the interface, it will not break through the interface.

The invention relates to a high-voltage insulator (1) comprising a long rod-type insulator (10) having a shaft (11) and circular shields (12) which are arranged thereon, comprising an insulator cap (2) at the top end of the long rod-type insulator (10) for fastening the high-voltage insulator (1) to a high-voltage mast, and comprising an arc protection ring (3) which surrounds the insulator cap (2) or that portion of the long rod-type insulator (10) which is situated closest to the insulator cap (2), wherein at least the topmost shield (12) of the long rod-type insulator (10), which shield is situated closest to the insulator cap (2), is designed as a protective shield (12) for the other shields (12), wherein the maximum diameter of the other shields (12) is at least 30 mm smaller than the inside diameter of the arc protection ring (3), the diameter of the at least one protective shield (12) is at least 10 mm smaller than the inside diameter of the arc protection ring (3), and the diameter of the at least one protective shield (12) is at least 20 mm larger than the maximum diameter of the other shields (12).

A polymer bushing includes: an inner conductor; a hard insulating tube; a shielding metal fitting; a polymer covering that includes a body part that covers an outer periphery of the insulating tube, and a plurality of umbrella-shaped sheds that are formed at an outer periphery of the body part; and an electric-field stress-control layer that is composed of a zinc oxide layer or a high-permittivity layer, and is disposed along an interface between the insulating tube and the polymer covering. A rear end part of the electric-field stress-control layer is connected to the shielding metal fitting. The body part includes a first body part that has a uniform thickness, and a second body part that is located in a region around a front end part of the electric-field stress-control layer and has a thickness greater than the thickness of the first body part.

A polymer bushing includes: an inner conductor; a hard insulating tube; a shielding metal fitting; a polymer covering that includes a body part that covers an outer periphery of the insulating tube, and a plurality of umbrella-shaped sheds that are formed at an outer periphery of the body part; and an electric-field stress-control layer that is composed of a zinc oxide layer or a high-permittivity layer, and is disposed along an interface between the insulating tube and the polymer covering. A rear end part of the electric-field stress-control layer is connected to the shielding metal fitting. The body part includes a first body part that has a uniform thickness, and a second body part that is located in a region around a front end part of the electric-field stress-control layer and has a thickness greater than the thickness of the first body part.