Patent ID: 7939752

Claim:
An elongated member, comprising: an outer sleeve-like rigid insulator shell; a high voltage conductor extending in a longitudinal direction of the shell and surrounded by the shell; a gap inside the shell next to an internal wall of the shell at least partially surrounding said conductor; and a medium comprising a material having electrically insulating properties arranged in the gap, said medium comprising an electrically insulating material comprising hollow spaces at least partially filled with gas, wherein said material is adapted to expand upon a temperature rise thereof by reversibly compressing said hollow spaces and reducing the volume thereof, wherein said hollow spaces comprise deformable spheres adapted to after deformation resume their shape when external compressive forces from said material are reduced as a consequence of a temperature decrease, wherein said material comprises a cross-linked gel including microspheres embedded therein, and wherein said microspheres are filled with a mixture of liquid and gas, in which the gas content is adapted to increase with the temperature of said material and thereby of the microspheres.