Device for electric field control

1. A device for controlling an electric field at a high voltage component comprising:

an inner deflector to be electrically connected to a live high voltage part of the high voltage component;

a resistive layer adapted for field controlling purposes, to be arranged along said high voltage component, and which at one position is to be connected to the live high voltage part of the high voltage component and at one end is adapted to be electrically connected to a grounded part of the high voltage component, the resistive layer having a nonlinear current-voltage characteristics;

an insulating layer arranged on said resistive layer and extending at least from said one position towards said one end of the resistive layer while ending without reaching said one end of the resistive layer; and

a semi-conducting or conducting layer arranged on the insulating layer and extending at least from said one position towards said one end of the resistive layer and past the end of the insulating layer, thereby defining an outer triple point at the intersection of the resistive layer, the insulating layer, and the semi-conducting or conducting layer, characterized in that

the resistive layer has first, second, and third adjacent sections as seen from said one position towards said one end, wherein

a portion of the first section extends below said inner deflector; and

said insulating layer is in contact with, and extends above, said inner deflector.

2. The device of claim 1 , wherein the first section has a maximum thickness, which is smaller than a minimum thickness of the second section.

3. The device of claim 2 , wherein the first section is a thin uniform layer of a substantially constant thickness.

4. The device of claim 1 comprising a connector, via which said inner deflector is to be electrically connected to said live high voltage part of the high voltage component.

5. The device of claim 4 wherein said portion of the first section, which extends below said inner deflector, is in contact with said connector only, with said inner deflector only, or with both the connector and the inner deflector.

6. The device of claim 4 wherein a portion of said insulating layer ( 6 ) extends below said inner deflector.

7. The device of claim 1 wherein

the third section is extending from the outer triple point to said one end; and

the second section has at least in a substantial part thereof tapered field control geometry with a gradually increasing thickness in the direction towards the outer triple point.

8. The device of claim 1 wherein the third section has, at least in a substantial portion thereof, a gradually decreasing thickness in the direction towards said one end.

9. The device of claim 8 wherein the portion of the third section, in which the thickness is gradually decreasing in the direction towards said one end, extends from the outer triple point to the end of a ground part of the high voltage component.

10. The device of claim 8 wherein the rate of the thickness decrease is decreasing in the direction towards said one end.

11. The device of claim 1 wherein the resistive layer is thickest at the outer triple point.

12. The device of claim 1 wherein

said device is arranged for controlling an electric field at a further high voltage component;

said inner deflector is to be electrically connected to a live high voltage part of the further high voltage component;

said resistive layer is to be arranged along said further high voltage component, and which at one further position is to be electrically connected to said live high voltage part of the further high voltage component and at one other end is adapted to be electrically connected to a grounded part of the further high voltage component;

said insulating layer is extending at least from said one further position towards said one other end of the resistive layer while ending without reaching said one other end of the resistive layer;

said semi-conducting or conducting layer arranged on the insulating layer and extending at least from said one further position towards said one other end of the resistive layer and past the end of the insulating layer, which does not reach said one other end of the resistive layer, thereby defining a further outer triple point at an intersection of the resistive layer, the insulating layer, and the semi-conducting or conducting layer;

the resistive layer has fourth, fifth, and sixth adjacent sections as seen from said one further position towards said one other end, wherein

a portion of the fourth section extends below said inner deflector.

13. The device of claim 12 wherein

the high voltage component and the further high voltage component are each a high voltage cable; and

said device is provided for jointing the high voltage cables in a cable joint.

14. The device of claim 1 wherein

the high voltage component is a high voltage cable, switchgear, or a vacuum breaker; and

said device is provided for terminating said high voltage cable in a cable termination or for being used as a bushing.

15. The device of claim 1 wherein said device is provided for controlling an electric field at a high voltage component, which is rated 300 kV or higher, or optionally 500 kV or higher, and which optionally is a DC high voltage component.

16. A device for controlling an electric field at a high voltage component comprising:

an inner deflector to be electrically connected to a live high voltage part of the high voltage component;

a resistive layer adapted for field controlling purposes, to be arranged along said high voltage component, and which at one position is to be connected to the live high voltage part of the high voltage component and at one end is adapted to be electrically connected to a grounded part of the high voltage component, the resistive layer having a nonlinear current-voltage characteristics;

an insulating layer arranged on said resistive layer and extending at least from said one position towards said one end of the resistive layer while ending without reaching said one end of the resistive layer; and

a semi-conducting or conducting layer arranged on the insulating layer and extending at least from said one position towards said one end of the resistive layer and past the end of the insulating layer, thereby defining an outer triple point at the intersection of the resistive layer, the insulating layer, and the semi-conducting or conducting layer, characterized in that

the resistive layer has first, second, and third adjacent sections as seen from said one position towards said one end, wherein

a portion of the first section extends below said inner deflector; and

a portion of the first section has a gradually decreasing thickness in the direction towards the second section.

17. The device of claim 16 , wherein the portion of the first section, which has a gradually decreasing thickness, is located at an end of the inner deflector.

18. The device of claim 16 wherein the portion of the first section, which has a gradually decreasing thickness, is located at a distance from an end of the inner deflector in the direction towards the second section.

19. The device of claim 16 wherein another portion of the first section is in contact with, and extends above, said inner deflector.

20. The device of claim 16 wherein said insulating layer is in contact with, and extends above, said inner deflector.

21. The device of claim 16 comprising a connector, via which said inner deflector is to be electrically connected to said live high voltage part of the high voltage component.

22. The device of claim 16 wherein

said device is arranged for controlling an electric field at a further high voltage component;

said inner deflector is to be electrically connected to a live high voltage part of the further high voltage component;

said resistive layer is to be arranged along said further high voltage component, and which at one further position is to be electrically connected to said live high voltage part of the further high voltage component and at one other end is adapted to be electrically connected to a grounded part of the further high voltage component;

said insulating layer is extending at least from said one further position towards said one other end of the resistive layer while ending without reaching said one other end of the resistive layer;

said semi-conducting or conducting layer arranged on the insulating layer and extending at least from said one further position towards said one other end of the resistive layer and past the end of the insulating layer, which does not reach said one other end of the resistive layer, thereby defining a further outer triple point at an intersection of the resistive layer, the insulating layer, and the semi-conducting or conducting layer;

the resistive layer has fourth, fifth, and sixth adjacent sections as seen from said one further position towards said one other end, wherein

a portion of the fourth section extends below said inner deflector.

23. The device of claim 22 wherein

the high voltage component and the further high voltage component are each a high voltage cable; and

said device is provided for jointing the high voltage cables in a cable joint.

24. The device of claim 16 wherein

the high voltage component is a high voltage cable, switchgear, or a vacuum breaker; and

said device is provided for terminating said high voltage cable in a cable termination or for being used as a bushing.

25. The device of claim 16 wherein said device is provided for controlling an electric field at a high voltage component, which is rated 300 kV or higher, or optionally 500 kV or higher, and which optionally is a DC high voltage component.

26. A device for controlling an electric field at a high voltage component comprising:

a resistive layer adapted for field controlling purposes, to be arranged along said high voltage component, and which at one position is adapted to be electrically connected to a live high voltage part of the high voltage component and at one end is adapted to be electrically connected to a grounded part of the high voltage component, the resistive layer having a nonlinear current-voltage characteristics;

an insulating layer arranged on said resistive layer and extending from said one position towards said one end of the resistive layer while ending without reaching said one end of the resistive layer; and

a semi-conducting or conducting layer arranged on the insulating layer and extending from said one position towards said one end of the resistive layer and past the end of the insulating layer, thereby defining an outer triple point at the intersection of the resistive layer, the insulating layer, and the semi-conducting or conducting layer, characterized in that

the resistive layer has first, second, and third adjacent sections as seen from said one position towards said one end, wherein

the third section is extending from the outer triple point to said one end; and

the second section has at least in a substantial part thereof tapered field control geometry with a gradually increasing thickness in the direction towards the outer triple point.

27. A device for controlling an electric field at a high voltage component comprising:

a resistive layer adapted for field controlling purposes, to be arranged along said high voltage component, and which at one position is adapted to be electrically connected to a live high voltage part of the high voltage component and at one end is adapted to be electrically connected to a grounded part of the high voltage component, the resistive layer having a nonlinear current-voltage characteristics;

an insulating layer arranged on said resistive layer and extending from said one position towards said one end of the resistive layer while ending without reaching said one end of the resistive layer; and

a semi-conducting or conducting layer arranged on the insulating layer and extending from said one position towards said one end of the resistive layer and past the end of the insulating layer, thereby defining an outer triple point at the intersection of the resistive layer, the insulating layer, and the semi-conducting or conducting layer, characterized in that

the resistive layer has first, second, and third adjacent sections as seen from said one position towards said one end, wherein

the third section is extending from the outer triple point to said one end; and

the third section has, at least in a substantial portion thereof, a gradually decreasing thickness in the direction towards said one end.