Elongated member and use thereof

1. 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.

2. The member according to claim 1 , wherein said microspheres have a diameter of 10 micrometers-100 micrometers when not deformed.

3. The member according to claim 1 , wherein said gel comprises a silicone gel.

4. The member according to claim 1 , wherein said microspheres are expanded microspheres.

5. The member according to claim 1 , wherein said microspheres are filled with only gas.

6. The member according to claim 1 , wherein a total volume of said hollow spaces is at room temperature 10-50 percent of the total volume of said medium and accordingly of said gap.

7. The member according to claim 1 , wherein said medium is filled into said gap to have an overpressure therein, thereby influencing the internal wall of said shell, with a pressure P of 0<P<2 bar at room temperature.

8. The member according to claim 1 , wherein said conductor comprises a conductor tube extending through substantially the entire shell.

9. The member according to claim 1 , wherein said gap separates the internal wall of the shell from an active core of the member comprising said conductor.

10. The member according to claim 9 , wherein said active core comprises electrical field distributing capacitors surrounding said conductor.

11. The member according to claim 1 , wherein said shell comprises a ceramic or polymer sleeve.

12. The member according to claim 11 , further comprising:

metal flanges secured to ends of said ceramic or polymer sleeve.

13. The member according to claim 1 , wherein the member is designed to have said conductor on a system voltage of at least twelve kilovolts.

14. The member according to claim 1 , wherein the member is designed to have a current of at least one amp to flow through the conductor thereof.

15. The member according to claim 1 , wherein the member is a bushing designed for leading the high voltage conductor through a wall.

16. The member according to claim 15 , wherein the member is a bushing to be arranged at a high voltage converter station for leading a high voltage conductor through a wall of a current valve hall and outdoors or from one such hall to another such hall.

17. The member according to claim 15 , wherein the member is a bushing adapted to be connected to the outer casing of any high voltage apparatus.

18. The member according to claim 17 , wherein the member is a bushing adapted to be connected to a high voltage disconnector.

19. The member according to claim 15 , wherein the member is a transformer bushing or a generator bushing.

20. The member according to claim 15 , wherein the member is a wall bushing.

21. The member according to claim 1 , wherein the member is designed to be arranged on a circumference of a bushing for leading the high voltage conductor through a wall for tapping a voltage from this bushing.

22. The member according to claim 1 , wherein the member is designed as a cable termination adapted to have the high voltage cable connected to one end thereof.

23. 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, said medium comprising an electrically insulating material comprising hollow spaces at least partially filled with gas, said material being adapted to expand upon a temperature rise thereof by reversibly compressing said hollow spaces and reducing the volume thereof, said hollow spaces being formed by 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, said material comprising a cross-linked gel including microspheres embedded therein, 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.

24. The member according to claim 23 , wherein a total volume of said hollow spaces is at room temperature 10-50% of the total volume of said medium and accordingly of said gap.

25. The member according to claim 23 , wherein the member is a wall bushing.

26. The member according to claim 23 , wherein the member is a transformer or generator bushing.

27. The member according to claim 23 , wherein the member is a cable termination.

28. The member according to claim 23 , wherein the member is a high voltage apparatus.