A first opposing surface inclination angle of a protruding first solid insulating material of a first high-voltage device is smaller than a second opposing surface inclination angle of a dented second solid insulating material of a second high-voltage device. A hollow truncated-cone flexible insulating material of which the thickness before insertion between the first high-voltage device and the second high-voltage device is the same at every part and the elasticity modulus gradually increases from a small-diameter side toward a large-diameter side, or a hollow truncated-cone flexible insulating material of which the thickness before insertion gradually increases from a small-diameter side toward a large-diameter side and the elasticity modulus is the same at every part, is compressed and sandwiched between the first solid insulating material and the second solid insulating material.

A submersible electrical enclosure is for a switchgear assembly. The switchgear assembly includes a number of electrical switching apparatus. The submersible electrical enclosure includes: a plurality of sides defining an interior, the interior receiving each of the electrical switching apparatus, each side including: a conductive polymeric layer facing away from the interior, and an insulative polymeric layer molded to the conductive polymeric layer. The insulative polymeric layer faces the interior and substantially overlays the conductive polymeric layer.

A submersible electrical enclosure is for a switchgear assembly. The switchgear assembly includes a number of electrical switching apparatus. The submersible electrical enclosure includes: a plurality of sides defining an interior, the interior receiving each of the electrical switching apparatus, each side including: a conductive polymeric layer facing away from the interior, and an insulative polymeric layer molded to the conductive polymeric layer. The insulative polymeric layer faces the interior and substantially overlays the conductive polymeric layer.

A gas-insulated switchgear includes a grounded tank filled with insulation gas, a center conductor which is disposed in the grounded tank and to which a voltage is applied, an insulating support member which insulates and supports the center conductor, and a nonlinear resistive part disposed at least on a vertically lower side inner surface of the grounded tank and formed by an insulation material containing a nonlinear resistive material. If an electric field applied to the nonlinear resistive part is higher than an electric field value in a vicinity of a contact point between the nonlinear resistive part and a metallic foreign substance mixed in the grounded tank during an operation, a resistivity of the nonlinear resistive part at the center conductor side is lower than a resistivity at which a discharge delay time is equal to an electric field relaxation time constant.

A gas-insulated switchgear includes a grounded tank filled with insulation gas, a center conductor which is disposed in the grounded tank and to which a voltage is applied, an insulating support member which insulates and supports the center conductor, and a nonlinear resistive part disposed at least on a vertically lower side inner surface of the grounded tank and formed by an insulation material containing a nonlinear resistive material. If an electric field applied to the nonlinear resistive part is higher than an electric field value in a vicinity of a contact point between the nonlinear resistive part and a metallic foreign substance mixed in the grounded tank during an operation, a resistivity of the nonlinear resistive part at the center conductor side is lower than a resistivity at which a discharge delay time is equal to an electric field relaxation time constant.