High voltage bushing, a method of cooling a conductor thereof, and an electric power distribution system comprising such a bushing

1. A high voltage bushing extending in a sloping, non-horizontal direction comprising

an elongated electric conductor,

a tubular insulator surrounding said conductor, and cooling means for cooling said conductor,

characterized in that said cooling means comprises one cooling element extending along a fraction of the length of said conductor and in thermal connection with said conductor and said cooling element is located at a first and upper end region of the bushing.

2. A high voltage bushing according to claim 1 , characterized in that said cooling element is thermal contact with a heat absorbing medium.

3. A high voltage bushing according to claim 1 , characterized in that said conductor is tubular with a longitudinal channel extending through it, and that said cooling element is arranged in channel.

4. A high voltage bushing according to claim 1 , characterized in that said cooling element is in direct contact with the conductor.

5. A high voltage bushing, according to claim 1 , characterized in that said cooling element defines a closed space with an opening for introduction of a cooling medium into said space.

6. A high voltage bushing according to claim 5 , characterized in that said cooling element also has a second opening for the discharge of a cooling medium from said space.

7. A high voltage bushing according to claim 1 , characterized in that said cooling element comprises a tubular body.

8. A high voltage bushing according to claim 7 , characterized in that said conductor is tubular with a longitudinal channel extending through it, and that said tubular body has an outer mantle surface which is in supporting and thermal connection with an inner periphery of said conductor.

9. A high voltage bushing according to claim 1 , characterized in that said cooling element comprises a body of metal in thermal connection with said conductor.

10. A high voltage bushing according to claim 1 , characterized in that it comprises a first conduit extending from an opening of the bushing to a cooling medium inlet opening of said at least one cooling element.

11. A high voltage bushing according to claim 10 , characterized in that said conductor is tubular with a longitudinal channel extending through it, and that said conduit extends inside said longitudinal channel.

12. A high voltage bushing according to claim 10 , characterized in that it comprises a second conduit extending from an opening of the bushing to a cooling medium outlet opening of said cooling element.

13. A high voltage bushing according to claim 12 , characterized in that said conductor is tubular with a longitudinal channel extending through it, and that said second conduit extends inside said longitudinal channel.

14. A high voltage bushing according to claim 12 , characterized in that each of said first and second conduits is formed by a hose or pipe separate from the conductor and extending inside said channel of the latter.

15. A high voltage bushing according to claim 1 , characterized in that it is provided with connection means for the connection thereof to a cooling system by means of which a circulating and heat absorbing cooling medium is thermally connected to said at least one cooling element upon operation of the bushing.

16. A high voltage bushing according to claim 15 , characterized in that said cooling medium comprises a liquid.

17. A high voltage bushing according to claim 1 , characterized in that the conductor is mounted in opposite ends of the insulator, and that there is provided a gas-filled space between the inner periphery of the insulator and the outer periphery of the conductor along the latter between said ends.

18. A method of cooling a conductor of a high voltage bushing which extends in a sloping, non-horizontal direction, said bushing comprising an elongated electric conductor and a tubular insulator surrounding said conductor, characterized in that the conductor is locally cooled along a fraction of the length thereof at a first and upper end region of the bushing.

19. A method according to claim 18 , characterized in that the conductor is cooled by means of circulating a cooling medium to a thermal contact with a cooling element provided at said fraction of the length of the conductor.

20. An electrical power distribution system, characterized in that it comprises a bushing according to claim 1 .