Air entrance bushing for gas-insulated bus

A gas-insulated bushing comprising, in combination:

• an axially elongated hollow insulation shell filled with gas under pressure;
• a conductive mounting flange fixed to one end portion of said insulation shell;
• an elongated high voltage conductor extending along the axis of said insulation shell and terminating at the end of said insulation shell opposite said one end portion and being connectable to regions external of said insulation shell;
• a gas-filled grounded cylindrical enclosure disposed coaxially with said insulation shell and connected to said flange;
• said elongated conductor having a portion thereof extending beyond said flange and into said cylindrical enclosure and along the axis of said cylindrical enclosure;
• insulation support means fixed within said cylindrical enclosure supporting said elongated conductor with respect to said enclosure and with respect to said insulation shell;
• and a hollow conductive shield having one end connected to said flange and to said cylindrical enclosure and being coaxial with said insulation shell and with the axis of said elongated conductor and extending from said one end of said insulation shell and into the interior of said insulation shell;
• the opposite end of said conductive shield having a diameter substantially smaller than either that of said one end of said shield or that of said insulation shell, the space between said opposite end of said conductive shield and said elongated conductor being filled solely with said gas, whereby the dielectric stress in said gas within said insulation shell in the annular region between said opposite end of said shield and said central conductor when said bushing is in operation is greater than the stress at any other region within said bushing.