Bushing equipped with an optical fibre
The invention is concerned with a bushing for high voltage applications and a bushing arrangement including such a bushing. The bushing includes a conductor defining a longitudinal axis (A) through the bushing where the bushing has a central section and a first and a second peripheral section on opposite sides of the central section along the longitudinal axis (A) and includes an optical fibre with a first part (P 1 ) stretching through the central section, the fibre being adapted to detect physical properties being influenced or caused by the operation of the bushing. The sections are sections of a solid condenser core and the bushing further includes an enclosure for a length of fibre that is to exit the bushing, the enclosure being buried in the central section adjacent the surface of the condenser core and having an interior volume.
1. A bushing for high voltage applications comprising a conductor defining a longitudinal axis (A) through the bushing,
said bushing having a central section and a first and a second peripheral section on opposite sides of the central section along the longitudinal axis (A), and
comprising an optical fibre for detecting physical properties being influenced or caused by the operation of the bushing and having a first part (P 1 ) stretching through the central section, wherein the sections are sections of a solid condenser core and further comprising an enclosure for a length of fibre that is to exit the bushing, said enclosure being buried in the central section adjacent the surface of the condenser core and having an interior volume with an inner surface comprising at least one point (P) at a maximum radial distance from the longitudinal axis, said enclosure comprising a distancing element keeping the length of fibre at a pre-determined distance (D) from said point,
wherein the enclosure comprises a first and a second chamber, where the second chamber is radially further away from the longitudinal axis than the first chamber, which comprises the length of fibre and is separated from the second chamber by a central wall which central wall forms the distancing element.
2. The bushing according to claim 1 , wherein the fibre exits the bushing via a flange surrounding the central section.
3. The bushing according to claim 1 , wherein the second peripheral section comprises a first end joined to the central section and a second end defining an end of the bushing through which the central conductor exits and said fibre comprising a second part with at least one first straight segment (P 2 A) stretching outside of the condenser core along the condenser core surface between the first and second ends of the second peripheral section.
4. The bushing according to claim 3 , wherein the first straight segment (P 2 A) stretches all the way between the first and second ends of the second peripheral section.
5. The bushing according to claim 3 , wherein the first straight segment starts (P 2 A) at the first end of the second peripheral section, stretches a length along the condenser core surface and is joined with a second straight segment (P 2 B) returning back to the first end of the second peripheral section.
6. The bushing according to claim 1 , wherein the bushing comprises a number of foils (F 1 , F 2 , F 3 , F 4 , F 5 , F 6 , F 7 , F 8 ) of conductive material, wound around and coaxial with the conductor, where the length in the longitudinal direction of any foil on a radial distance from the conductor is shorter than the foil length of any neighboring foil on a lower radial distance from the conductor.
7. The bushing according to claim 6 , wherein the first part (P 1 ) of the fibre comprises a number of turns of fibre wound around the central conductor between different foils (F 1 , F 2 , F 3 , F 4 , F 5 , F 6 , F 7 , F 8 ) of the central section.
8. The bushing according to claim 7 , wherein the radial distance of the turns increase from a first end of the first part in a first area where the central section joins the first peripheral section towards a second end of the first part in a second area where the central section joins the second peripheral section.
9. The bushing according to claim 8 , wherein the sections are sections of a solid condenser core and the turns in the first part (P 1 ) stretch from being placed between an innermost foil (F 1 ) and the conductor to being placed between an outermost foil (F 8 ) and the condenser core surface.
10. The bushing according to claim 9 , wherein each turn encircles an area that is angled in relation to the longitudinal axis (A) of the conductor so that one point of a turn is closest to the second peripheral section and an opposite point of the same turn is closest to the first peripheral section.
11. The bushing according to claim 6 , wherein the first part (P 1 ) of the fibre comprises turns having the same radius and being placed between the innermost foil (F 1 ) and the conductor.
12. The bushing according to claim 6 , wherein the fibre comprises a third part (P 3 ) in the first peripheral section joined with the first part, said third part having turns with the same radius and being placed between the innermost foil (F 1 ) and the conductor.
13. The bushing according to claim 6 , wherein the fibre comprises a fourth part (P 4 ) in the second peripheral section joined with the first part, said fourth part having turns with the same radius and being placed between the innermost foil (F 1 ) and the conductor.
14. A bushing arrangement comprising the bushing according to claim 1 and at least one detector configured to detect physical properties of the bushing influenced or caused by the operation of the bushing.