Gas-insulated electric device

A gas-insulated electric device having a pressure tank being electrically grounded, in which insulation gas is encapsulated, and a bushing, in which one end portion is hermetically fixed to an aperture of the pressure tank and the other end portion is sealed by a terminal conductor so as to encapsulate the insulation gas, in a state where a central conductor of the bushing is inserted from the bushing into the pressure tank, the gas-insulated electric device comprising:

• an insulation tube vertically disposed that ranges to portions facing to ground potential portions for the central conductor and to upper-lower portions along the grounding potential portions, and is coaxially arranged along the central conductor in a state where a vertically through gap intervenes between the central conductor and the insulation tube along an entire length of the insulation tube;
• a conductive layer that is formed on an inner surface of the insulation tube facing the gap and the central conductor and electrically connected to the central conductor;
• and
• a ground layer that is formed in an inside of the insulation tube or on an outer surface of the insulation tube and is grounded;
• wherein the gap between the central conductor and the insulation tube connects an internal space of the pressure tank and an internal space of the bushing, and
• wherein heat generated from the central conductor is radiated by convecting the insulation gas through the gap and passing the insulation gas through the gap from one end of the gap to an other end of the gap, thereby the insulation gas in the internal space of the pressure tank flows via the gap into the internal space of the bushing.