Wall bushing

A wall bushing for high voltage application, the wall bushing comprising a grounded shield, the grounded shield comprising a grading ring in a distal end thereof, the grading ring having an elliptic cross section with conjugate diameters, wherein a major diameter of the conjugate diameters is arranged in an axial direction of the grounded shield and a minor diameter of the conjugate diameters is arranged in a radial direction of the grounded shield, wherein the major diameter is larger than the minor diameter, wherein the major diameter is between 10 and 55% longer than the minor diameter, and wherein a shortest distance between the grading ring and a grounded flange comprises about a same distance between the grounded shield and the grounded flange.